Edit errors since updating to 5.6.3.4

Permalink
Currently updated to 5.6.3.4

When editing a block, I get 2 different errors:
1: in yellow when the WSIWG edit window is open:
This block is an alias of Page Defaults. Editing it here will "disconnect" it so changes to Page Defaults will no longer affect this block.
2: after editing and "Save", a window pops up in red:
An unexpected error occurred. Unable to get permission key for write< Back to Home
I can refresh the page, the window goes away, and the edits DID take, but this has to happen every time I want to edit. The client will freak seeing this.

Any suggestions for a fix?