Migrating to a new core using replication

Morning,

I have a core I'll call the "old core" with four agents that replicates to an off site core. The "old core" is having hardware issues so we installed a "new core", setup repositories etc etc and enabled Y shaped replication. Once that completed we were going to follow the procedures to move the protection to the new core and setup replication to the off site core.

Three of the four agents replicated to the new core with no issues, in fact it was quite fast over the LAN. One agent, the Exchange server, is generating errors and will never complete. The first error that showed up indicated there was something wrong with the repository. I did some searching and it pointed to the retention periods not being the same on the two cores. Not sure why that only affected one agent but we fixed that and tried again. Below is the error that now shows up:

An exception was caught while trying to deserialize the encapsulated exception of type 'System.AggregateException'
Attempted to access an element as a type incompatible with the array.
So I don't know if I should troubleshoot that error or just move on and transfer the protection of the three working agents to the new core and then push out protection to this one missing agent and let it do a full backup. I will of course lose the existing backups but it might be faster in the long run.
So my question is, should I continue to work on this error or just move forward and protect this agent on the new core?
Thanks for any advice.