When Ozzy's anal gland ruptured a few months back, the vet told me if he happened again, to bring him in regularly and have them completely drain it.
They explained to me that at the Groomer's, they only relieve the glands externally. At the vet's, they relieve it internally so all of the fluid is expelled. Have they suggested trying this? (Depending on test results).
You could probably also have your vet show you how to do it and you could do it yourself. (Though I'm sure you know it's messy and smells less than lovely).
Ozzy - Chocolate Pom
-Fastest 2012 U-FLI Pomeranian
"In a perfect world, every dog would have a home and every home would have a dog."