Corrupted files from version 4.1.2 to 4.2

Hello to MuseScore community!

I have created scores in fantastic version 4.1.2, mostly from scratch. But all my files saved in this format (4.1.2) are corrupted when opened in new version 4.2. They can look OK in page mode, but in horizontal continuous view, there are enormous black spots (like filled slurs) from place to place. It seems that there are problems with ties across measure bars: even after having removed manually those huge spots, I am unable to restore ties as those black things reappear.

See for instance the two attached files:
- Beethoven's piano sonata n°17, Op. 31 third movement
- Antonio Vivaldi's Nisi Dominus: saved in page mode, appearance is OK; but if you display the sore in continuous mode (horizontal) those filled black slurs appear

Please correct urgently this really annoying bug.

Thank you in advance