Signals on slope removed when using «auto remove on construction» with dragging

[Rau117]

Version of OpenTTD

Found on 1.11.0-beta2
Tested on nighty20210303

Expected result

Signal is removed only where the branch can be built

Actual result

Signals are removed wherever the path is planned

Btw signal is not removed if you click once on sloped track.

Steps to reproduce

Build some tracks with signals on slope, try to build new tracks across this slope with dragging