Definitely update the skin, but do it with jAlbum not running. Go to https://jalbum.net/skins/skin/Turtle/ and click Install skin. Once it's downloaded, double-click the Turtle.jaskin file on your PC to install it. Then you can launch jAlbum and open your project.
When making the album, make absolutely sure that you have not told jAlbum to process only updated subdirectories. It needs to process all of the subdirectories. There's no need to force it to reprocess all the images - as long as you haven't done something like changing the image bounds, the images will be fine. In either case, just click Make Album and let jAlbum figure out what needs to be done.
That's a lot of versions to be jumping over, though, so there may be some surprises I haven't thought about.
ETA: I see that your current album was made with Turtle 5.6.4, and the current version is 5.6.6, so that shouldn't present any problems. The jAlbum core update won't make much difference in how the album is generated, though it will probably be a lot faster!
Somewhat off-topic, but there appears to be an interesting bug in the Turtle background music player controls. It shows up if you try to pause/unpause the music. I'll have to tinker with it a bit, but that may be something to bring up in the Turtle forum section.
ETA: Confirmed that it's a skin problem, and posted a report about it in the Turtle section.
One more thought. Jumping over that many jAlbum versions also means that it's using a much newer version of the Java image processor. The first time you make the album, it may actually need to reprocess all the images, so don't be surprised if the first build takes a little time, followed by an equally long upload (since all of the image files will be "new").
All but the most recent content predates the digital age and are typically "snapshots" taken with rudimentary cameras.
Paper prints were scanned, as were 35mm and 6 x 6 trannies - and negs. where available . . .
Most all were passed through "The Gimp" to get the best out of them - so the Album represents a fair amount of "work" in its preparation.
Yes, I've got a website of family stuff where a lot of the pre-digital raw material is pretty grubby. And without a very high-end scanner, dealing with old Kodachromes is an exercise in frustration. The prints scan better, but you certainly can't push them very far.
Some of the oldest stuff turns out to be the best. Instead of being shot with someone's Brownie, the late-19th Century photos were professional studio products, so they're sharp and clear!
Indeed so. Getting the old stuff into a suitable form can be trying.
I held on to my Scanner - an Epson Perfection 1200 Photo - for this reason.
It can (also) scan negs and trannies up to 4" x 5" . . . .
Annoyingly, Epson stopped Driver support ~ Vista, so I bought the VueScan software - (which I recommend), and it worked perfectly with Win7 Pro and later Win10 Pro . . .
Not really high-end, but does the job . . . .
My grandfather was keen photographer, did his own D&P (as you did back then) . . . I have boxes of his glass plates . . .
He took this with his 1/4-Plate Sanderson . . . .
Conspicuously "Posed", the Newspaper reports on the Funeral of General Booth the previous day, (you can READ it on the original neg) which suggests THIS was taken the following day - August 30th, 1912 . . . . Other items of interest are the Lemonade bottle with the captive "marble" closure, The Bass® Triangle on the beer bottle (Registered Trade Mark No 000001 here in the UK). My Father is looking away from the camera, next to his brother, with their sister in the Pram . . . and my Grandmother (imagine getting dressed up like that, just for a picnic?)