I am uncertain if I got everything, but this whole situation sounds very weird.
I have a very strong feeling there are problems way underneath the effects you see.
I am talking misconfigurations, misunderstandings and maybe even modifications under the hood.
Without a live view on the environment it will be impossible to give definitive statements though.
But I am very certain, that the solutions you describe should not be necessary to replace a failed Checkmk server. Far from it. It is very straight forward if there was no tampering.
Anyway, I am glad you could fix your situation.