/replaceitem does not work when hooked up to a fill clock, only when you re-log you get the replaced item

When I attached a few command blocks to a fill clock that has the command /replacitem expected it will constantly replace the leather armor in your armor slots with new leather armor to make the armor never go away.

To test this I turned on the clock and there it was, the leather armor I wanted, but once I took off the armor, there was none replace back into that slot. When I went into the fill clock command blocks, they were working and also the command block that is issuing the /replace item commands were also outputting but I did not get my leather armor I wanted.

I then took a break, left the game and came back later. When entered the game, amazingly I had the armor again! But the same issue encountered before happened again (when I took it off it did not regenerate)

I hope you can fix this bug so I can finish my minigame I have been working on! Thanks!