When trying to put a 4x4 belt balancer over the 4 lane bus, underground some extra underground belts are placed for some reason.
This is how a balancer loosk like:
This is what it looks like without force building while hovering:
And this is what it looks like after I use force building:
The part of the reason may be that force building doesn't overwrite the parts with air tiles in the pasted content. This is a separate issue though and could be a feature request.
Considering that only non-air tiles are replaced, in my opinion it should look like below after force building instead (notice that it would also be broken, but only due to existing belts being skipped due to empty tiles in the clipboard):
[2.0.10] force building belts over other belts adds extra unwanted underground belts
[2.0.10] force building belts over other belts adds extra unwanted underground belts
Look mom, I made a mod ^^ Barrel Stages