The /fill command appears to be partially broken with fences.

1. When using /fill with fences, it always displays as a success, with all the blocks being placed, even if nothing changes.

This is weird because if you use the command to fill in spaces with blocks, it recognizes that nothing changed and, therefore, displays that no blocks were filled.

2. If you use /fill, break a fence, and repeat the command, the fences around it act funny and don't connect like usual.

From my testing, it appears that the effects are always to the south and to the east. Chunk borders and the shapes of the holes don't appear to affect them.

Attachments of my testing are provided.

This may be related to MC-129367.