I won't be very popular with MikeK... The version listed is I think Current Branch 1606... which is out of support... unless that company is paying for extended support?
https://learn.microsoft.com/en-us/lifecycle/products/microsoft-system-center-configuration-manager-ltsb-version-1606
"In general", unless the RLA (Replication Link Analyzer) fixes the issue, there are 'usually' deeper issues which will require a support call, and a forum won't be able to help you fix the issue. Compounded with the fact that you seem to be running a 6 year old version , out of support (2022 - 2016 = 6 years)... you might be in a pickle, MikeK