Changes to a score cause all fermatas over a barline to be discarded
Documented on Forum post https://musescore.org/en/node/270849
This seems only to affect fermatas which are placed over the barline (select the barline before clicking on the fermata). Such fermatas are saved successfully, but a subsequent change to the score (e.g. adding stave text of style Tempo in next bar) will result in all such fermatas and the new text being discarded when the file is saved, closed and reopened.