I could not find this one; also not sure if it belongs in this section but I saw a few more relating to tabs so here it goes.

1. Compile a sketch with multiple tabs.
2. Rename one of the cpp tabs (I renamed both a cpp and h file and adjusted the main sketch accordingly).
3. Compile again.

The result is an error about multiple definition of the functions where the original object file is mentioned.

Current workaround is to close and open the IDE (using version 1.8.5)