It looks like there is a problem between the Gutenberg plugin and the current WP core 5.1.1.
When I disabled the Gutenberg plugin (and classic editor as well) I created a new post. As I was typing the title and error message box overlayed with the message,
“The editor has encountered an unexpected error” and then 3 buttons: attempt recovery, copy post text, copy error.
I clicked attempt recovery, I’d be back in the draft post, a second later the same error message.
I discovered this issue “possibly” after 5.1.1 updated. I publish my podcast from my posts via the Bluburry PowerPress Plugin. Please note that plugin HAS NOT updated in some time, and my ability to upload media via the post plugin functionality has been working for the last 9 months
When I reactivated the Gutenberg plugin, and then did a test to upload a media file to Bluburry via the PowerPress plugins available in the post, I get this error message:
“Fatal error: Call to a member function is_block_editor() on null in /home/eatmove5/public_html/darrenstehle/wp-content/plugins/gutenberg/lib/widgets.php on line 13”
Now, the only way I can upload media files is the the plugin “Classic Editor” installed, and Gutenberg disabled.