Routing issue directly behind tunnel portal

[Sique]

Simutrans 125.01
Pak 64x64 r12234

Maybe, I'll manage to upload screenshots in the future, but right now, I get a file too large error.

Situation:
I have a trainstation and a rail crossover directly in front of a tunnel portal, and within the tunnel, the rail branches immediately after the tunnel.

========\/U----
========/\U----
############`---

Legend:
= train station tile

\/
/\ Interconnection between parallel rails

U tunnel portal

` branching off

# Empty space for formatting

A train that comes in from the East into the northern platform of the train station unloads, changes direction and leaves the train station via the cross over back into the tunnel. The routing seems to be unable to route the train on the branching rail. Instead, the train continues straight after entering the tunnel.

If I put the branch one tile later, the train routing finds the branching off rail.

PS: I found a similar routing issue after a slope. Also there, trains don't necessarily find the branch. What's curious is that some do, and some don't, albeit they are running on different routes. And in both cases, it was a train carrying cars, consisting of a pair of DB Br 218 pulling four Laekks553 (a/b) units. But that last fact might be random.