Exchanging Gadget for slabs on bottom half not working

[rannday]

Building Gadgets Version
1.0.7

Describe the bug
Trying to replace slabs placed on the bottom half of a block only replaces the top half of the slab. Bottom half still removed, but new/replaced slabs are on the top half.

To Reproduce
ATM9 To the Sky - 1.1.1 - Replace slabs on the bottom portion.

Expected behavior
Replace the slabs on the bottom half, not the top.

Screenshots