Text substitution problems

I've had some issues with the built in text substitutions on Apple devices, especially on my iPad. The main problem has been duplicates and the fact that when I tried to delete the duplicates or other items, they always come back automatically after a while. I have tried to delete the unwanted items many times. Sometimes those items spread to my other devices, and sometimes they only stayed on the iPad. I recently tried to clean everything up on all of my devices. I deleted all unwanted items on all of them, and I made sure that some other changes propagated to all of them. Some changes took a few days to get all of my computers, but for now at least, they are all the way they should be, and so is my iPhone. The iPad also stayed in its desired state for several days, but then all the deleted items reappeared like so many times before. Is there anything I can do about this? I have tried turning off iCloud before and then turning it on again. Also some reset methods a while ago, but never from scratch which I would prefer not to do. Is there a way to reset only this part of iCloud?

Another problem I have from time to time is that the substitution stop working. Usually if I go in and add a new substitution, they will start working again.