Another obscure issue I ran into not long ago was when using MySQL Workbench, and clicking on a table, it became stuck in fetching mode.
What triggered the issue was a recent MySQL upgrade, but MySQL itself, not Workbench.
After checking the error log, we saw an error like:
Incorrect definition of table mysql.proc: expected column 'comment' at position 15 to have type text, found type char(64)
Instantly, I knew mysql_upgrade needed to be ran in order to fix the “Incorrect definition” issue, and turns out that is the root cause for Workbench getting stuck in the “fetching” mode.
So the solution is to run mysql_upgrade. Should that not fix the table for some reason, then you can also fix it alternatively with:
ALTER TABLE mysql.proc MODIFY `comment` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL; FLUSH TABLES;
Hope this helps.