yes
It has nothing to do with a GPS tool, only with panoramic images.
It did work a long time, but somewhere in time this problem was created. The user panel code is not changed the last 2 years, so I can't explain why I get now a silent crash. Nevertherless the parameters in the panel are correctly saved.

I couldn't resist having a fiddle with this. Between knowing that my own custom UI code doesn't call saveUI() at all (it's no longer necessary), and swiping some error-checking from ctwist's Mirage code, I arrived at this:

import java.awt.SystemColor;
import java.util.HashMap;
import javax.swing.*;
import se.datadosen.component.JLabelFor;
import se.datadosen.component.StateMonitor;
import static se.datadosen.component.StateMonitor.enable;
import se.datadosen.jalbum.AlbumObject;
import se.datadosen.jalbum.AlbumObjectProperties;
import se.datadosen.jalbum.Category;
import se.datadosen.jalbum.JAlbumContext;
import se.datadosen.jalbum.JCustomPanel;
class DemoSkinCustom extends JCustomPanel {
// Fields
    JCheckBox isPano = new JCheckBox("Panoramic");
    JSpinner custMaxImageWidth = new JSpinner(new SpinnerNumberModel(5000, 3000, 50000, 1000));
// Set up custom UI panel
    public DemoSkinCustom(JAlbumContext context) {
        super(context);
// Listeners
        new StateMonitor() {
            public void onChange() {
                boolean isImage = currentAO.getCategory() == Category.image;
                enable(isImage && isPano.isSelected(), custMaxImageWidth);
                AlbumObjectProperties currentProps = currentAO.getProperties();
                HashMap<String, Object> currentUserVars = (HashMap<String, Object>) currentProps.get("userVariables");
                if (isPano.isSelected()) {
                    if (currentUserVars == null) {
                        currentUserVars = new HashMap();
                    }
                    currentUserVars.put("maxImageWidth", custMaxImageWidth.getValue().toString());
                } else {
                    if (currentUserVars != null) {
                        currentUserVars.remove("maxImageWidth");
                    }
                }
                if (currentUserVars == null || currentUserVars.isEmpty()) {
                    currentProps.remove("userVariables");
                } else {
                    currentProps.put("userVariables", currentUserVars);
                }
                currentProps.save();
            }
        }.add(isPano);
// Spinner format
        custMaxImageWidth.setEditor(new JSpinner.NumberEditor(custMaxImageWidth, "#####"));
// Layout
        setBackground(SystemColor.text);
        setOpaque(false);
        add(isPano);
        add("br", new JLabelFor("Max image width", custMaxImageWidth));
        add(custMaxImageWidth);
// Init
        init();
    }
    public void setAlbumObject(AlbumObject ao) {
        if (ao != null) {
            super.setAlbumObject(ao);
            boolean isImage = currentAO.getCategory() == Category.image;
            isPano.setEnabled(isImage);
            custMaxImageWidth.setEnabled(isImage && isPano.isSelected());
        }
    }
}

This enables a Panoramic checkbox in the edit panel only for images - disabled for folders, videos, etc., where it would make no sense. If you check the box, you can use the spinner to select a width. That action populates the user variables with an entry for maxImageWidth (not visible unless you close/open the edit panel, or move to the next object, but it's there nonetheless). If you uncheck the box, that value is removed from the user variables.

If the user manually removes the user variable, the image-specific maxImageWidth is no longer applied unless he toggles the Panoramic checkbox - the skin can't overcome all the odd things a user might do.

Tested, and it all seems to work.

Well I don't know how you tested it, but I added it to the onload.bsh file of my FancyBox skin and got this error:
bsh.ParseException: Parse error at line 76, column 31. Encountered: , in onload.bsh at line number 76

I don't know how to correct this line 76:

HashMap<String, Object> currentUserVars = (HashMap<String, Object>) currentProps.get("userVariables");

The jaskin file is enclosed.

Anyhow many thanks for your work!!

Not so pessimistic, with some additions I have it running in onload.bsh:

class DemoSkinCustom extends JCustomPanel {
// Fields
    JCheckBox isPano = new JCheckBox("Panoramic");
    JSpinner custMaxImageWidth = new JSpinner(new SpinnerNumberModel(5000, 3000, 50000, 1000));
// Set up custom UI panel
    public DemoSkinCustom(JAlbumContext context) {
        super(context);
// Listeners
        new StateMonitor() {
            public void onChange() {
                boolean isImage = currentAO.getCategory() == Category.image;
                enable(isImage && isPano.isSelected(), custMaxImageWidth);
                AlbumObjectProperties currentProps = currentAO.getProperties();
                //HashMap<String, Object> currentUserVars = (HashMap<String, Object>) currentProps.get("userVariables");
                HashMap currentUserVars = (HashMap) properties.get(AlbumObjectProperties.USER_VARIABLES);
                if (isPano.isSelected()) {
                    if (currentUserVars == null) {
                        currentUserVars = new HashMap();
                    }
                    currentUserVars.put("maxImageWidth", custMaxImageWidth.getValue().toString());
                } else {
                    if (currentUserVars != null) {
                        currentUserVars.remove("maxImageWidth");
                    }
                }
                if (currentUserVars == null || currentUserVars.isEmpty()) {
                    currentProps.remove("userVariables");
                } else {
                    currentProps.put("userVariables", currentUserVars);
                }
                currentProps.save();
            }
        }.add(isPano);
// Spinner format
        custMaxImageWidth.setEditor(new JSpinner.NumberEditor(custMaxImageWidth, "#####"));
// Layout
        setBackground(SystemColor.text);
        setOpaque(false);
        add(isPano);
        add("br", new JLabelFor("Max image width", custMaxImageWidth));
        add(custMaxImageWidth);
// Init
        init();
    }
    public void setAlbumObject(AlbumObject ao) {
        if (ao != null) {
            super.setAlbumObject(ao);
            boolean isImage = currentAO.getCategory() == Category.image;
            isPano.setEnabled(isImage);
            custMaxImageWidth.setEnabled(isImage && isPano.isSelected());
        }
    }
}
 
 
// Make some convenient references available
JAlbumContext context = JAlbumContext.getInstance();
PluginContext pc = context.getPluginContext();
EditPanel editPanel = pc.getEditPanel();
 
DemoSkinCustom DemoSkinCustom = new DemoSkinCustom(context);
// Install custom panel in Jalbum's edit panel
editPanel.addCustomTab("Panoramic image", DemoSkinCustom);
/*

Now I have to add user variable "pan360".

Edit:
There is a problem: the edit window shows no image, only a black background.

This is caused by the statement:
HashMap currentUserVars = (HashMap) properties.get(AlbumObjectProperties.USER_VARIABLES);

Edited by: AndreWolff on 22-Jul-2019 19:04

Until now I tried to prevent a silent crash after using your tool by changing something in my skins, without success.

Now I tried to change something in your tool to prevent a silent crash.
This was more successfully: by removing the setAccessibility statements the silent crash is gone!

The corrected tool is enclosed.

Well if I remove both setAccessibility(true); and setAccessibility(false); all works fine,
but with only setAccessibility(false); outcommented it works also fine.

What do you mean with that?
I tested my modified version of your tool with other skins like the Tiger skin and it works there also perfect.