This is the report I just sent to Mozilla Feedback:
Twice it has crashed while I was editing pages on Wikipedia. This may be related to the fact that, at least on this device, when I paste material into a location with a lot of text after it -
often unavoidable in Wikipedia's current beta mobile front end, which only supports editing at the h2 level of a page - the screen jitters for a long time, consistent with sending each
character to the server add and refreshing the screen for that one-character edit.
I believe those were both on Talk:National Film Registry, but, sorry, I can't be certain. I am pretty sure they were both on the same page.