Except for the monitor's refresh rate, those specs are fairly similar to our dev PC. Is there any way you could underclock the monitor it to check if the game functions properly at 60hz?
I've been messing with the nvidia control panel, but still haven't been able to reproduce the bug yet. I will keep trying in the coming weeks while I work on implementing an actual graphics menu. Perhaps see if there's any sort of logging or diagnostics I could sneak in to gather more information. Sorry the game's not working for you!