[2.1.17] Weird placing of belts while dragging + rotating

[damadmax]

Steps to reproduce:
1. Select a belt
2. rotate to south
3. click&drag about 10 tiles
4. drag mouse back about 5 tiles
5. press R to divert direction
6. drag either east or west

Expected:
the result should imho be a L-shaped belt

Actually:
an L-shaped belt appears, but additionally many perpendicular aligned belt tiles appear

[Loewchen]

128470

[damadmax]

[facepalm]