Is it possible that some services, miners and users are just running older versions of terracoin, and the forks are caused by the frequent hardforking updates to the difficulty adjustment algorithm?
I'd say
many are still using old wallets. Coinotron is updated, but still closed for TRC mining.
People seeing difficulty below 5255 are on an orphaned chain and should update their client
ASAP (this is the minimum difficulty supported by the latest client).