Hey Alëna,
I think the big one is business versus customer. If PM is charged with realising business value, then their view can be skewed. If UX is charged with delivering customer value, then their view can be skewed.
Ultimately the balance between the often competiting priorities is the biggest challenge (IMHO).
I’ve found embedding economics into the design process helps. It gives the design team a way to speak the same language as the PM and a lot of the rest of the business. This shared understanding (from my observation) leads to deeper, more effective collaboration.
A slightly less obvious observation is that this shared understanding seems to result in more balanced, alinged goals across these functions. It’s somewhat self perpetuating. Fascinting too :)