My reproducer:
1. Make sure no libreoffice programs are running
2. Start writer, blank document
3. Confirm that HUD is working, e.g. Alt, "i o f" brings up Insert > Object > Formula
4. Insert a formula in the new document, leave the formula editor, back to document
5. Confirm that HUD is not working anymore, e.g. Alt, "save" does not bring up File > Save as would be expected
I am seeing exact same behavior as Till is.
My reproducer:
1. Make sure no libreoffice programs are running
2. Start writer, blank document
3. Confirm that HUD is working, e.g. Alt, "i o f" brings up Insert > Object > Formula
4. Insert a formula in the new document, leave the formula editor, back to document
5. Confirm that HUD is not working anymore, e.g. Alt, "save" does not bring up File > Save as would be expected