Using VirtualBox latest version in KDE Neon. Debian VM was running quite well till yesterday, when suddenly I faced laggig. I could move the cursor, but it wasn't registering any clicks. And for some time, the PC altogether became unresponsive. As a result, couldn't get out full screen mode(finally did using Sup+D), Virtualbox GUI was also unresponsive. So killed that VM instance using terminal. After restarting, faced the same issue after a few minutes. Today installed a new Virtual Machine, and that too is having same problem. Any solution to this click thing? It's becoming unusable!

I have guest os extension installed, host to guest clipboard on. BTW, no dnd was enabled, pointing device is kept as USB-tablet.