Here's what is happening for me, and it happens a lot.

On facebook, have clicked on the link to upload a photo. Photo starts to upload, and I start to write a caption. Opera crashes.
After Opera restarts, photo uploads and all is fine.

Does not happen every time but possibly 1 in 4.

Version information

Version: 47.0.2631.55
Update stream: Stable
System: Mac OS X 10.12.6 64-bit