Hi,
I think you’d better use the jump message :
InsertSendMessage fx1 1 Jump 41310
It is the same, but InsertControllers messages are deprecated and may disappears at a moment…
That said, I can’t reproduce your issue here.
Of course, you need to jump to a position that is inside your selection.
If you jump outside of the selection, the playing head is set to the beginning of the selection…
Do I misunderstood someting?
Philippe