Building Issue

Just wondering if anyone else has any issues while building? I cant seem to replace an existing structure. For example, if I have a grass floor already built, if I try to replace it with bur, im not able to deposit any materials into it without having to go underneath. This is the case with any floor and happens with walls too sometimes. I cant seem to find any solutions or any one else having this issue anywhere unless I just suck at looking.

EDIT: This is before and during the current PTB