When adding a location or organizer in their own form (not from the event form dialog), after pressing the "Add new..." submit button, the spinner keeps spinning endlessly and there is no feedback to the user that the data is actually saved; but it is correctly saved.
Thanks :O)
P.S.
I believe this started happening with 5.0.9 but I can't be sure because I usually only add organizers and locations right in their add event form respective sections, and since 5.0.9 created the "click outside the form and forma and data disappear" I started to add locations and organizers in their own forms to avoid accidental data loses; and that's when I discovered this issue.