Try doing a SVN Cleanup. I had the same issue and after doing that the locks cleared up.
Specifically from the Tortoise SVN Cleanup Documentation:
If a Subversion command cannot complete successfully, perhaps due to
server problems, your working copy can be left in an inconsistent
state. In that case you need to use TortoiseSVN → Cleanup on the
folder. It is a good idea to do this at the top level of the working
copy.In the cleanup dialog, there are also other useful options to get the
working copy into a clean state.Clean up working copy status As stated above, this option tries to get
an inconsistent working copy into a workable and usable state. This
doesn’t affect any data you have but only the internal states of the
working copy database. This is the actual Cleanup command you know
from older TortoiseSVN clients or other SVN clients.
Here is a screenshot of the recommended SVN Cleanup options:
