Did anybody ever get tot the bottom of this? if not I have some further information, and I wish all those who are persisting with it the best.
I ran into this after upgrading our setup from a raspberry Pi running OLP 2.4.6 to a new Windows 11 machine Try as I might I couldn't get the new machine to open any previous service files.
I ended up doing a binary search on versions to see which one causes the problem. The error has been introduced in between V2.9.0 and 2.9.2 (I couldn't run 2.9.1 as the installer doesn't work and it refused to boot) versions 2.9.0 and lower would open all tested previous service files versions over 2.9.2 failed ALL previous service files.
From this point on I'm talking about creating a presentation in OLP 2.9.0 and trying to open in in the latest release version 3.1.
I noticed an error when opening v 2.9.0 that the images plug-in was failing to load. So i deliberately did a fresh install with the old user data folder renamed so as to create a totally clean installation. I thin copied across all the databases from the old to the new data folder for everything except the images so as to allow me to create a test service. This went well and it opened in OLP 3.1.
I then added in Two copies of the same image into the presentation and et voila when opened in 3.1 I got the corruption message appearing and the import stopped when loading the second image.
Also interestingly from that moment on My v2.9.0 install became a random exception generator again. but that's another slightly different story.
I hope this proves useful in tracking down the problem. Sadly this is the last time you'll see me on here as I can't await for a fix after two weeks of total bedlam and my ears burnt with complaints I've had t succumb to the closed source world.