Thanks for the replies, folks.

Some further observations:
- it's not a lag issue
- not only happens with broadcast but also with Ulaa's suggestion up top and also the built-in Follow Me and Interact With Target
- IWT spammed for melee teams can pretty reliably cause this problem each encounter
- more often affects same account(s) consistantly during a session but not the same account(s) across different sessiosn

I'm wondering if it could be a FPS issue?