x-factors and abilities disappear in some MUT Solo Challenges

I also took notes while playing the Zero Chill challenges released on Dec. 14th.

I played challenges in 6 'series' (i.e. the first game from each series was started from the menu 'Challenges' while I started the next challenges using the option 'play next challenge' directly after finishing the previous challenge) and the bug occured in 3 of them:

1. played challenges: 2, bug appeared in the 2nd challenge (maybe in the first already without notice)
2. played challenges: 6, no bug 
3. played challenge: 1, no bug (end of 'Mr Grouch')
4. played challenges: 5, bug appeared in 5th challenge
5. played challenges. 4, bug appeared in 3rd and 4th challenge
6. played challenge: 1, no bug (end of 'Mutville')

summarising: the bug occured in 3 out of the 6 series I played to complete the first two sets of Zero Chill Solo Challenges. In total, I had 4 games without x-factors nor abilities. if I did not stop the series as soon as the bug appeared for the first time (i.e. going back to the menu and newly loading into the challenges) I would have had 4-5 Solos with x-factors and abilities and 14-15 Solos without x-factors/abilities (incl. the repetitions of a few Solos to collect all available bonus stars. the '4-5' results from the fact that I cannot exactly remember whether the bug was already there in the very first Solo).

frankly, the bug simply occurs far too often!

UPDATE: in the 3rd Zero Chill solos series ('Who's Sandersclaws?') the bug did not occur.