Currently played 5 challenges (watering, archers, picking, hoeing and chopping) and won all 5.
I'm suspecting that my picking-challenge didn't get recorded as hoeing started with 6 malus applied (2 keys won).
Checking my e-mails, I only have 4 confirmations.
Checking my prize list, I only have 4 new ones.
Gonna try grabbing some screenshots from here on.
Edit:
Failed sickling with 12 malus (57/60, suggest lowering requirement)
Succeeded at mining at 13/12 with 12 malus and 5 seconds to spare.
Challenge was concluded at 12:40:06 local time (UTC+1). (Screenshot of the "win"-message was taken 5 seconds after the challenge was concluded.)



Edit: Loading up the next challenge, malus is still at 12s (4 keys won), same as it was before the last win.
Current status:
7 challenges played
7 challenges won
4 keys received (both inbox and prize list supports this.)
No sign of that "Inconsistent Data"-error today though, so that's a good sign at least.