Wall bells cannot be placed on the stone side of floor bells, despite having enough support

It is not possible for a wall bell to be placed on the stone sides of a floor bell, despite having enough support.

Steps to Reproduce

1. Build this structure:

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2.  Try to place wall bells on the stone sides of any of the floor bells.

Expected Results:
A wall bell is placed on the stone sides of the floor bell.

 Observed result:
The wall bell cannot be placed on the stone sides of the floor bell.