Did you check in this tread?

https://www.gog.com/forum/jagged_alliance_series/113_modd

And might not be related, did you install directx 9.0c?

Also:

The same was somewhere posted here on GOG, but nevertheless just copied from a steam thread:

1. Download the v1.1.38 Version of the programm:

http://download.savannah.nongnu.org/releases/wined3d

2. Download the wined3d.exe
3. Extract It with 7zip or other extract-programm.
6. Copy ddraw.dll, libwine.dll and wined3d.dll from extracted $SYSDIR folder into the root folder of your JA2_wildfire installation.

This works for me on Windows 10 64bit.

Some more hints can be found in here, like deleting certain .slf files.

https://steamcommunity.com/app/215930/discussions/0/535150948592034575/?ctp=2

And Yes that was the program mentioned somewhere here as well and I hope it helps ;)

Thanks mate for the replies and hints. Some of this I have done. I'll dig through the threads and see if I missed anything. From the Steam thread I gather the fixes work for some and not others. The three .dlls fixed my problem with the frame rate. And it isn't crashing on start up, like another mentioned.

I'll keep digging. Definitely helps. :)

New laptop...decided to work through a game of JA2 w 1.13. Yeah, well Windows 10 had other plans. I ended up working out all the other bugs using the included fixes that come with 1.13. However, one thing persisted. The game would freeze anywhere from 2 to 20 minutes after start. Basically unplayable.

My fix was to set processor affinity to use only 1 processor (Processor 1, but I doubt that matters) for the JA2.exe once you start up the game. Now I've played several sessions for a few hours and it works perfectly.

It took me quite a while to find mention of this in some thread...I've since forgotten where...so I'm posting it here.