It's possible to get very unlucky with random sometimes.

For instance, even though the farm horse has a 30% chance to drop a key, it might be possible to go many turns without it dropping if you're really unlucky (as someone experienced).

So, having drop failsafes or making drops happen on a sliding scale would help with this -- especially for the key items.

ex: Increase probability 1/4 => 2/4 => 3/4 => 4/4 for key drop items like farm key