[kovarex] [1.1.12] Drag placing adds unexpected undergrounds during quick movement over existing ones

[bormand]

Follow up on 94375

1) Build a belt with underground (top part of the the screenshot)
2) Hold LMB to begin drag-upgrade
3) Quickly shake mouse around existing undergrounds

Actual: unexpected undergrounds appear
Expected: nothing happens

Intuition tells me that this would be fixed together with 94488 since it needs quick motion and can't be reproduced with a slow one.

Screenshot from 2021-01-17 00-49-04.png (111.81 KiB) Viewed 688 times

[kovarex]

This has (almost surely) the same cause as this 94488
I extended some of the test to be more sure (but can never be completely).