I am using on the UCM this version 10.5.2.12900-14 and in the IM and Presence this one 10.5.1.10000-9.
I have downgraded to version 8.5.1 on the Expressway and all is working fine. There is not problem with other Expressway functionalities (B2B calls) in the version 8.5.3 but with the RMA, we have two pairs of Expressway, for the JabberGuest and B2B environment we have the 8.5.3 Expressway version and all seems to be working fine, for the RMA environment we have the version 8.5.1.
I'm having same issue. CUCM and IM&P are on 10.5(2). Exp-C and E are on 8.5.3.
Will try to downgrade and see how it goes.
Edit: Issue resolved after downgrading.
Upgraded -C and -E to version X8.6 today, not getting the error about Cluster not found.