First, I have seen the a similar bug report on Java edition. But I couldn't find a Bedrock one.

I am making a map, so I have a lot of repeating commands and they just stop working randomly, I read that there's a bug about using /clone command and that would cause the repeating commands to stop working, so I basically removed them, and instead used structure blocks. But it's the same effect, the always active repeating commands stop for no reason. The only thing I can do is to turn them off and on or place another one, which is pretty difficult cause there is a lot of them. Hope you can get this fixed soonC:.

PD: I have found some bug reports about the same thing but they aren't resolsolved:O

Edit: So I am on the 1.14.60 version, this bug still exsists. I discover one cause of this bug, and when you load a really big structure from a structure block (for example a 64 x 60 x 64 structure) suddenly all commands just stop working.  So I really don't know how it works but I suppose that it's because memory fills up in your computer and to load all the structure, it just uses all of the memory. Like I said, I really don't know how Minecraft works, but this is a really bad problem. So if you could fix it soon it would be cool.