Since you’re previewing a Stacks page, it’s reasonable there’s a good chance it’s Stacks. But what’s the next step…
Report the bug
If there’s a crash, send/share/post a crash report. Sometimes with just that info alone a crashing bug can be resolved. Sometimes more info is needed too – so any other details, screenshots, and info you can provide is great. If you can detail the exact steps which can get from a new-file to a crash then that’s a big help too.
Work around the problem
After you’ve reported the crash – which generally means making the problem happen MORE and recording/documenting/etc – you’ll want to try to make the problem happen LESS. Doing that generally involves some critical thinking and deductive problem solving. Try following this post and seeing if you can nail down the root cause and eliminate it – just temporarily – until the bug is fixed. That’s why we call it a work-around. Just like you drive around a pot-hole – or even taking a different street – until the city work-crew comes and fixes the road.