Just ran a test but cannot observe any buggy symptoms. Did you change anything in that schematic that could trigger a buggy condition? Alternatively, upgrade your trust level to a basic user and upload the schematic that might be causing the issue.
Qspice Forum - New User to Basic User (File Upload) - QSPICE - Qorvo Tech Forum
I personally have reported several cases where the waveform viewer crashes. Typically, these reports are sent via email to Mike Engelhardt, which can be found in Qspice > Help > About. My approach is to include the schematic (.qsch) that can replicate the problem and record a short video to demonstrate to Mike what the crash process looks like.
Based on your description, you are running a long simulation. How large is your .qraw data file after the simulation is completed? Is there a possibility that you are working with a file that is up to tens or hundreds of gigabytes in size?