G3 breaks my OT code

Here’s my prototype font for Kwekor script, encoded in PUA for the time being.

In G2 my conjuncts work fine:

In G3 they don’t work:

The lookups are in a prefix, then called in the CCMP feature. Might that be somehow treated differently in G3?

Does anyone have an idea why that happened? The OT compiler got changed again?

Can you call me?