After upgrading to the latest version of SQL Developer (22.214.171.124), I had a similar experience as the one listed here:F9 key not working anymore (Execute Statement shortcut)
That is, my F9 key was not working. In my case, however, it seemed to be running a script (the expected behavior of F5). Following the advice in the above post, I went here: Tool --> Preferences --> Shortcut Keys
I then saw the following:
Command: Run Statement
So It looked like "run statement" was still mapped to "F9". Yet, when I manually re-mapped it to F9, the original behavior was put back in place. So even if it looks like a key is still mapped to what it should be, a remapping may be helpful.