When you manually resume a coroutine you bypass our engine’s resume implementation resulting in continuations not being processed. This means anything waiting on your script to return will wait forever. It’s not strictly a bug more of a side-effect of the way things are implemented. You can see my response to a similar issue here.
We are unlikely to ever fix this, but you can actually handle it yourself. You can use task.spawn as a drop in replacement for coroutine.resume and things will automatically work as you expect 