I have the same issue, so here it is step by step:
1. log in (into wordpress backend)
2. create new location
3. log out
4. view map and/or list with all locations -> result: new location is not shown (this is a bug since 5.5.4)
5. log in
6. create an event for the new location
7. log out
8. view map and/or list with all locations -> result: new location is shown as there is an event set in the database
9. log in
10. delete the event for the new location
11. log out
12. view map and/or list with all locations -> result: new location is shown as there is a deleted event set in the database
13. log in
14. empty the trash events (with the deleted event for the new location)
15. log out
16. view map and/or list with all locations -> result: new location is not shown as the only event had been removed from the database
P.S.: When logged in, locations map/list will always show correctly, so this issue will only appear for logged out and therefore visitors.