When approaching a level crossing in this situation, are you obliged to stop the vehicle before the STOP sign?

Why?

The visible B-20 STOP sign requires you to stop before the railway crossing, but the signpost itself does not mark the stopping point. Stop at the marked stop line or, if there is none, before the crossing where you can see along the tracks and check for an approaching train. The answer 'no' concerns stopping before the sign itself, not an exemption from stopping.

§ 21 ust. 2 i 4 rozporządzenia w sprawie znaków i sygnałów drogowych