Trapped primary motion

Question for anyone that might have the same issue: I have a trapped primary motion. All of my tests are reasonably fast (220-ish), and I can usually play a rhythmically steady tremolo at 190-ish, up to 210bpm on a good day. My motion however is a direct back and forth across the string, which leaves me fully trapped and unable to execute string crossing. I’m currently working with Joao to try and fix it, but it seems harder to ‘reprogram’ rather than learn a new skill. I’ve gone through the primer and didn’t see anything specifically addressing trapped motion.

Has anyone had a similar experience? If so, how did you fix it? Thanks for any advice!