For some reason, Sometimes when using /fill on Chain Command Blocks, it doesnt work.

Say i have 2 Chain command block lines, both lines of chain command blocks have the same /fill commands with the same coordinates. Now there are 6 command blocks in each line, each of which fill different areas of a Room.

Above is a shot description of my Setup, Im trying to fill a room using different chain lines. In a way Im making a room that changes. And for SOME REASON, whenever i run the fill command on 1 line of command blocks, it works on that portion of the room, but when I go to click the other chain, the same coordinates that I edited, physically stop working, and i have to re-paste the fill command in, and when I run THOSE command blocks... It suddenly works and the other one that USED to work will suddenly stop working....

Its like the chain command block's ability to place blocks... seems to... switch between the two for some reason

(Keep in mind these commands are directly tested by myself, then pasted into the command blocks, so I know they work by using them in chat, but the command blocks themselves have trouble running them...)

Its very difficult to explain it, so I've included a copy of the world file for tests, to do the glitch with the world I included, flip the Levers on End Portal and then try the lever on the sign Empty (the room [output of the command blocks] where the changes occur should be behind you when the world is opened)

The World .zip (its too big for the attachment) (I hope its okay and not against any rules that I provide this link to google drive for my world)

https://drive.google.com/open?id=1Y1R-_scEnF9JX_0b75loiPziPhjyiTaj