I'm not coming from Devuan but Xubuntu 16.04, but maybe my answer can help you a bit...

I had the exactly same problem as you - having a nvidia card (NVS310) and firefox (54.0.4 64bit in my case) crashing on drag/drop and telling me "Request 141.8: BadWindow..." on the command line. I could reproduce the problem with thunderbird, too (the problem seems to be GTK-related).

In my case it was the nvidia-driver (regardless which version - I tested nvidia-384 and nvidia-340). When switching to nouveau the problem disappeared - but unfortunately I cannot use nouveau for other reasons...

Thanks to a colleague I could circumvent the problem in a completely unexpected way - by disabling "display compositing" in XFCE. You can find it under Settings->'Window Manager Tweaks'->Compositor. Now I can drag/drop again as usual without any crashes.

I know that this is not a real solution to the underlying problem, but it works for me while waiting for a real one.

HTH
Kuni