BasvandenBerg: I tested it with my controller and it has the same problem. So it's not just the keyboard. Has anyone found a solution yet? I can't find anything.
I contacted support and with some back and forth messages spanning days, I tried everything I could think of. From uninstalling programs, disconnecting and removal of drivers of all controllers on my system, different install locations, different permissions, adding to firewall, installed in safe mode and clean boot mode, created a Windows 10 Virtual Machine to install to make sure nothing was affecting the games install, I tried a different keyboard, unplugging the keyboard and plugging back in after the game loaded, dropping the summers exe directly on to the dosbox exe, windowed, full screen, different resolutions, different refresh rates, replacing my config files with the config files the gog support representative provided me, and a few more different things that didn't work. I also installed on laptop we have but that also had the issue.
It's a very weird issue, support was unable to recreate the issue when they tried, and on a handful of times when I reinstalled the game (like 4 in a total of many many many more) I was able to have the game work as intended upon first load, but as soon as I close the game and load it back up again, the issue is back. And each time it worked, it seemed random.
In the end we couldn't find the resolution but they was going to forward all the information on to the QA team, so I'm hoping they can replicate the issue and find a fix.
It would be nice if they could jump in this thread though to let us know they are looking into it.