The gap occurs somewhere between utopis account history transaction 971 (the 20.424 transfer on 29/03) and utopis account history transaction 2015 (the 84.385 transfer on 10/05). So it's a gap of roughly 1000 transactions.

The account history API allows up to 1000 transactions to be pulled at a time. So getting a full account history requires a loop of batches of 1000 transactions. I'm guessing there's a problem either pulling or processing one particular batch.