I love the Reach Around Block Placement method but im noticing that if I try to use it with the mud block, it tries to place it one block down, then it disappears immediately. Heres the clip:

https://streamable.com/x1j2bu

also doesnt let you place other blocks (that do work) on the edge of mud blocks

Should be fixed now. When placing other blocks (blocks that are full size) around a mud block (or any other block that is not full size) you have to be positioned a bit further from the edge of the block so that your player hitbox does not conflict with the new full size block. Thanks for opening this issue!