I recreated this bug 2 times.

I was trying to display the "AffectedBlocks" stats of a clone command on the sidebar.
First I wrote the following command inside an Impulse command block.

clone ~ ~ ~ ~ 0 ~ -635 4 1452

When executed, this command should give (and indeed does, when you look into the "Previous Output" bar) the number of blocks between the command block and Level 0 as an AffectedBlocks output.

To achieve this, I applied the following stats-command on an armor stand called stats, while standing on top of the command block:

/stats block ~ ~-1 ~ set AffectedBlocks @e[type=armor_stand,name=stats,c=1] Coordinate

The stats were applied and I manually set the score of the armor stand for the objective "Coordinate" to "0", as this is necessary for the stats command to work.

I now activated the Impulse command and the number 5 was displayed on the scoreboard. The correct number of blocks between the command block and Level 0. I now changed the command to:

execute @a ~ ~ ~ clone ~ ~ ~ ~ 0 ~ -635 4 1452

When executed the command should give me the number of blocks between the player and Level 0, however the number on the side didn't change, the output of the command block (when you look inside it) did. It displayed the Output "[19:56:16] 4 blocks cloned".

When I changed it to the following command:

clone ~ ~-1 ~ ~ 0 ~ -635 4 1452

It again gave me the right output and it was displayed correctly on the sidebar.

I tried storing the stats-Command on different entities, using Repeat, Chain and Impulse command blocks and switching between worlds.