Command block set to repeat will randomly stop working.
I have been making a map for 5 months now with many repeating command blocks. I updated to 1.14.1 and whilst working on my map suddenly most if not all repeating command blocks stopped working. They would update if I turned them off and on again, or simply powered them with a redstone block. BUT again they stopped working. Luckily I made a back up, and I only wasted 7 HOURS of my life trying to work around it.
I am forced to stay in 1,14 until that issue is fixed.
Comments
Yeah, just ran into this same issue. I have a couple repeating command blocks set to always active that seemingly randomly decided to stop working running. Turning them off and on worked for me as well.
I can confirm that repeating command blocks stop working as soon as a /clone command is run off of a separate command block. It is not the case if the player executes the command via chat.
This bug is especially game-breaking for me as I'm on Realms and cannot simply revert back to 1.14.
My current workaround is to:
a) Have all of my repeating command blocks be in a centralized area (ie: spawn chunks).
b) Make all of my repeating command blocks require redstone to be activated.
and then (after every command block that runs a clone command) do:
1) /fill xyz1 xyz2 white_wool replace redstone_block
2) /fill xyz1 xyz2 redstone_block replace white_wool
This process reactivates all repeating command blocks within xyz1 to xyz2.
This issue appears to be fixed in 1.14.2

Not quite sure how to reply to people on this site. @Afro_Gizmo that might work? Have they said they fixed? Or they do it secretly? Also I see you're from Vancouver, nice! I'm near Burnaby.
@unknown Are you able to reproduce this issue in 1.14.2?

@Johnibur It looks like it is fixed in 1.14.2

while this bug is wreaking havoc on many worlds, there is a workaround that i found rather soon after 1.14.1 was released, and it is to summon entities with NoAI:1 and a CustomName in the chunks of any command block in the world. (i.e. if your chain spans multiple chunks, each chunk needs a new entity.)
/summon pig ~ ~ ~ {Silent:1,Invulnerable:1,Tags:[loader],CustomName:{"text":"loader"
}}
I also noticed that! In my case repeating command block stop working when any another command block successfully execute /clone command. Very strange behavior...