I don't know that show. I don't think we got it on this side of the pond.
I reckon what happens is (this is a little woo-woo of me haha)...
... we will figure out (have figured out in the future) how to edit events in the past by transmitting waves and signals back in time. I reckon these are experiments carried out in the future.
I think many of them succeeded, or succeed now that that they've mastered the science. The earlier experiments that failed or didn't quite edit everything (write errors and what not), are the ones we're experiencing as Mandela Effects :)

Now they edit things and we NEVER know, because everyone gets the "update".