Actor won't cross portal on poly if poly bumps into actor

[FishyClockwork]

If a line portal on a polyobject approaches/bumps into a stationary actor, the actor won't cross the portal. Instead the actor ends up behind the portal line. And if the portal line is one-sided (as is acceptable if it's on a polyobject) then the actor ends up in the "void space" or "inside" the polyobject. (Potentially getting stuck and needing to noclip out of there.)

It works fine, however, if it's the actor that approaches/walks over the portal line.

Looking at this, it appears to be a known problem.
https://github.com/coelckers/gzdoom/blob/bf3340338137f7c47dfb5cd95fe2ce36bc99e2be/src/playsim/po_man.cpp#L1112

Here's a test map demonstrating the problem. Just stand still and let the portal approach you.
There are 4 polyobjects. 2 with a two-sided portal line, and 2 with a one-sided portal line.