ZDoom

It's definitely just a folder change. I've seen it happen a number of times, and on this latest one it was due to how I decided to store both "Rowdy Rudy's Revenge" and "Rowdy Rudy Returns in POWERTRIP" in a single folder - on loading the first mod the saves no longer work. I hadn't gotten that far into the first mod, though, so ended up just deleting the saves and starting again.

Paths were never stored there. If you renamed a folder with mods while keeping filenames untouched, and saved games cannot be loaded, the problem is somewhere else. Did you check console output for loaded files?

[quote="_mental_"]There is no ready to use solution because coding a support for such corner case isn't worth the effort IMHO.
Although, you can edit saved game to make it work. A file with .zds extension is a regular .zip archive. It contains several files, but all you need is to edit [b]info.json[/b] accordingly.[/quote]
I don't know how to edit the info.json file to make it work as it doesn't appear to contain any kind of file path at all. Here's an example one from Operation Sea Wolf, one of the Winter Agent Juno mapsets.

{
"Software": "GZDoom g3.8pre-72-g3b77e2db6",
"Engine": "GZDOOM",
"Save Version": 4554,
"Title": "Dan",
"Current Map": "MAP04",
"Game WAD": "doom2.wad",
"Map WAD": "SWv1.3.pk3:sw command center.wad",
"Creation Time": "Sun Jan 6 2019 22:49:37",
"Comment": "MAP04 - Command Center\ntime: 00:02:08"
}

It refers to the filenames of the IWAD and PWAD (and in this case also a WAD file contained within the PK3) but no path.

There is no ready to use solution because coding a support for such corner case isn't worth the effort IMHO.
Although, you can edit saved game to make it work. A file with .zds extension is a regular .zip archive. It contains several files, but all you need is to edit [b]info.json[/b] accordingly.

So basically, if the IWAD and/or PWAD is moved (for instance in the example that I just experienced, I renamed a mod folder where I have the mod's .WAD file) then save files cannot be loaded by GZDoom as it gives the "different version" message. But the version of the WAD itself is no different.

Is there a way to force it to load the save file? I know the ECWolf has a --foreignsave command line parameter that can do this, and it is based on ZDoom, but I cannot find a similar option for GZDoom.