Strange VM window crashes

Hi, sometimes when I run some app (on XFCE), all of my windows crash in the VM (fedora), VM is still running but I cannot open any new windows (for example terminal or file manager). It fixes itself when I restart VM but it is uncomfortable when I do something important that I didn’t save.
Maybe someone knows how can I fix it?

Maybe it’s crashing if there is not enough free memory available in the qube. Try to increase the qube’s memory.