Since this seems like such an obvious bug, I wanted to check if other people also have it, or if something is wrong with my specific device.
I am no longer able to edit the names of maps. Not even when defining a new map, in which case the name is locked to "NewMapnik".
From the OsmAnd main screen, open the menu (bottom left), Configure map, Map source, Define/Edit. The Name field in this screen is read-only. Which now means I can only add one custom map, which will be named "NewMapnik". If I try to create another, it will just overwrite the previous.