Found in: ID 2022
If you have a table and put text into a cell, the text has at least one font assigned. When removing the text again, the cell becomes empty but seems to keep the font assignment, which is illogical. No text, no font. Later, if you open the document on another PC which doesn't have that font would cause a missing font issue for no reason.

Even worse: going into the "Find/replace font" dialog you can find the empty cell with the missing font, but you cannot fix it, because Change or Change all have no effect. The only way to change the font, because you cannot simply unassign, is to select the entire cell and set a font that is available . When you have, like, 100 empty cells it can be a very annoying job to do and might not be circumvented by selecting the entire table and setting the font when non-empty cells have several fonts assigned.