The bug

Inside of NPC dialogue files, commands that reference @initiator work fine when called directly. But when calling a function that references @initiator, it suddenly stops working.

How to reproduce

1. Download and open the attached world
2.

/dialogue open @e[type=pig,c=1] @p test

3. Click the button

Expected result
Both DIRECT and FUNCTION show "initiator" followed by your name

Observed result
Only DIRECT does, FUNCTION shows nothing, indicating the selector failed.
"did not find initiator" is a message for MCPE-165065.

Notes
This is not the same as, but may be related to MCPE-164727. That one only occurs when experiments are on.