With mirror modelling on, deleting or transforming perfectly centered geometry duplicates model

[Cub0use]

What are you trying to do, and what do you expect to happen?

Using mirror modelling.

What happens instead?

When editing faces perfectly centered (transforming or deleting), the geometry on both sides is mirrored, doubling the polycount. It only doubles the faces, not the vertices, judging by the model statistics.
(When deleting, with 1 plane selected, it first deletes 2 faces before doubling everything).

No error is thrown.

bb_bug_mirror_center_dup.mp4

It does not happen consistently: when deleting, it can also just recreate the faces on both sides:

bb_bug_mirror_center_cancelled.mp4

I imagine automatically merging the centered overlapping vertices on the initial mirror would solve the issue?

Model format in which the issue occurs

Generic

Blockbench variant

Program

Blockbench version

4.8.3

Operating System

W10

Installed Blockbench plugins

N/A