Xdcr 4.5 couchbase not replicating a document

I have a document on the primary cluster that is not replicating to the XDCR cluster. I have no idea how many other documents are not replicating but fear that there are a lot more. I’m using version Version: 4.5.1-2844 Community Edition (build-2844) on both sides. Any ideas on what cause is?

[xdcr:debug,2018-02-20T23:07:18.604Z,ns_1@10.125.136.176:<0.2859.3>:goxdcr_rest:stats:220]Unable to obtain stats for bucket “cmw” from goxdcr:
{error,{badmatch,{error,connection_closed}},
[{goxdcr_rest,send_with_timeout,5,
[{file,“src/goxdcr_rest.erl”},{line,61}]},
{goxdcr_rest,query_goxdcr,4,[{file,“src/goxdcr_rest.erl”},{line,141}]},
{goxdcr_rest,get_from_goxdcr,3,
[{file,“src/goxdcr_rest.erl”},{line,161}]},
{goxdcr_rest,stats,1,[{file,“src/goxdcr_rest.erl”},{line,216}]},
{goxdcr_stats_collector,grab_stats,1,
[{file,“src/goxdcr_stats_collector.erl”},
{line,37}]},
{base_stats_collector,handle_info,2,
[{file,“src/base_stats_collector.erl”},
{line,89}]},
{gen_server,handle_msg,5,[{file,“gen_server.erl”},{line,604}]},
{proc_lib,init_p_do_apply,3,[{file,“proc_lib.erl”},{line,239}]}]}

MassValidateVBUUID failed, err=Can’t find ‘mismatched’ in response

some how it has magically started to replicate … not sure why it falls it’s behind and then all of a sudden catches up.