I upgraded from iOS 12 to 13.3. Most things worked (Parental Controls/Screen Time may be more broken, but it’s always broken), but I had one significant bug.
If I opened a .docx (Word) file in Mail.app it would display in the docx viewer as expected. If I then tapped the share sheet icon the viewer would crash.
David Yeh found a workaround — do a long press on the document and then use the share sheet from that popup screen. Another contributor suggested removing and restoring the mail account, that didn’t work for me.
Today I found a fix for my case. I deleted two utilities: Pinner (last updated 2y ago) and Opener (frequently updated) then restarted my phone. That removed their associated share sheet action apps.
Now the share sheet works for me.
I’ll reinstall Opener if I find I miss it. Pushpin.app was updated relatively recently so I’ll use that instead of Pinner (really, I only use the Pushpin app action).