One month, they withdrew my mortgage twice on the same day (found out when my debit card declined at the grocery store).
They sent a mortgage interest statement in January. I filled out my taxes, then after I had gotten my refund, they sent a corrected mortgage interest statement. I had to make a judgement call on whether this required re-filing taxes and the expense that entailed.
The worst was when we got a $2500 check from the mortgage company, saying they had recalculated our escrow, and they had overestimated it initially. We spent most of that money on setting up a nursery for a new baby. Two months later, we received another letter saying, "whoops, our bad, we actually did have escrow calculated correctly the first time. Pay us $2500 in 30 days or your house note is going up by $200 a month until escrow is funded again".
EDIT: Recalled another issue with this company. I'd get e-mails monthly: "You're late on your payment. We're about to foreclose on your house". This would be followed by an e-mail: "Our computer system is being upgraded. Please disregard late payment e-mails if you've paid your mortgage. We should have this fixed within three months".
I refuse to let others handle my escrow, and pay taxes myself. I've had companies 'miss' tax payments, or pay the wrong amount, and I'm still stuck holding the bag, and potentially losing my house, but I didn't have the money to cover it - the mortgage servicer did.