Are you rolling with a gi on or no-gi?
I do both, but I'm in a gi more often than not.
I have the same problem sometimes. I've had some success with a move called a canopener. Basically you put both hands on the back/crown of their head and your elbows as close as possible together on their chest, and pull. In order to relieve the pressure on their neck muscles they need to sit up. This causes them to open their guard. From there I begin to work my pass.
This doesn't work all the time but it does give you an option to try when you get stuck or serve as a distraction. Good luck.
That's actually a really good one. I remember watching a Bas Rutten video on Youtube where he used it to escape from a triangle. I definitely gotta use it more often. Thanks man!
Anyone else got some good stuff for me?