The database would need to be updated. You will need to run a MySQL update command.
You might also need to delete the downloaded tiles. I seem to recall a similar issue on my own installation, but this was maybe 9 years ago. As I recall, if you have tiles downloaded, and the map bounding area either contained missing tiles or some other mismatch of the expected tiles, the CPU would run wild trying to do something when you tried loading the page for the first time.
Here's the code that handles the local maps.
I found this by searching the repo with this URL. Not sure, but I think you can follow this same link to see the same results.
// Select the database and run:
UPDATE settings SET value = '0' WHERE name = 'local_maps' LIMIT 1;