diff shoot up too quickly, need to let it stabilize. Blockchain works fine. The average block time is 1 min, with variations of course.
Difficulty keeps going up by the maximum even though blocks have been taking longer than a minute for some time now.
A difficulty of 20.9 is only correct for a one minute target if the network is hitting something like 1.4GH. Your reported network hash has been increasing monotonically and I'm betting will do so even if only a single miner is connected. I'd guess that you have some counter somewhere in the code that's incrementing but never resetting to zero like it's supposed to do.
Whatever the cause, broke coin is broken.