IDE showing unknown method with Step Into, which can't then be stepped further?

I’m experiencing a weird issue in one of my projects.
I’m setting the ListIndex of a PopupMenu and, as intended, this triggers the Change event, but not the one I expect (nothing behaves as the event code should)…

So I put a breakpoint at the ListIndex=0 line and then use “Step Into”. At this point, the IDE shows some code, taken from I-don’t-know-where.

The stack correctly shows this:
(by the way, it could be handy if the IDE allowed copy&paste for the tack…)

And the method signature is right too:
Sub Change(index as Integer)

But the remaining code isn’t the one found in the PMOperators’ Change event! I recognise it’s my style of coding, but even searching in the whole project for some words in this “fake” displayed event handler shows no result.

The highlighted line is, at tis point, the method declaration, since I haven’t yet stepped further. If I now step (over or into), the IDE switches to the correct event handler and highlights the first line. I can now step thru the correct method (but the behaviour I was debugging in the first place would indicate the event isn’t executed correctly anyway; this is still to be proven).

I’m not sure how to reproduce this in a simple project to demonstrate the issue (and fill a bug report), as I don’t even know where that “other code” comes from…

Any idea?