I did reach level 62 with playing partner on buddy challenge and over a weekend it reset us to level 1 suggesting we had failed to complete a challenge despite not being given one. I play the game at least once a day to collect candy drops for boosters so I know for a fact there was no buddy challenge available to play.
I contacted your Twitter support and was fobbed off with rubbish essentially saying hard cheese. I have just reached level 11 with same playing partner and the same thing has happened again when I went to play game this morning. What a joke