I was having this issue as well, in Firefox, and found a workaround. I disabled the hardware acceleration in Firefox and I have not had any issues thus far.
My system:
Windows 10 Version 1709
Firefox 58.0.2 (64-bit)
Avast Passwords version 1.1.3327
Avast Internet Security version 18.1.2326
How to disable hardware acceleration in Firefox:
Open Firefox
Open a new tab and type
about:preferences to open the preferences option page
On the General page, scroll down to the
Performance options
Uncheck the
'Use recommended performance settings' to see additional options
Uncheck the 'Use hardware acceleration when available'
Not sure if this will help anyone else but its a quick test and if it doesn't help you can just revert the changes by checking the 'Use recommended performance settings'
Good luck

-BB-