Sorry, for the late reply.
Actually, no, I don't want to kind of "work around" that issue, by manipulating my original files. IMHO I think that trying to read meta data from a PNG or PDF makes no sense in the first place. But that is not the point here.
The real problem is, that JA should only read
once meta data from a file. And it only should re-read the meta data, if the files changed the modified date. Just the way David described who it should work.
Cheers, Markus