Have you considered having the pet sitter stay with you for a few days or even a week before you leave, doing what he/she normally would do with the dog or dogs while you are there also?
With most dogs, it's just the change in routine that is upsetting. Tucker likes things to have things be the same all the time and even the smallest change can start a spiteful peeing spree, some unusual growling and other things.
We used to get a housesitter/petsitter to com stay at our condo when we still lived there and EVERY time when we got home we would find pee somewhere in the house and Tucker would pee in the house for days after, sometime weeks. Tucker did okay at the kennel, but after 3-4 days, he becomes incorigable even to the trained staff there. My stepfather passed several years ago right at the end of my alumni reunion weekend. Wife and I were in Charleston, had spent the weekend there and got the call as we were leaving town and had to divert to Greenville rather than home. We were away for 10 days and around day 6 or 7, Tucker started biting the staff back home at the kennel…