It looks like there's an update to a row on the publisher that is failing as the appropriate row cannot be found on the subscriber...

Your options are:

a) Skip these kinds of errors by including the "-SkipErrors 20598" switch in the distributor agent (not very recommended as you'll not know what kind of data issues you're having)

b) Locate the row on the publisher that is being updated, insert this row on the susbcriber DB. The update should then go through.

In replication monitory - when you see the error that the row was not found at the subscriber you will find the xact_seqno and the command_id as part of the error message...what you can do is this:

EXEC distribution.dbo.sp_browsereplcmds 'Put the xact_seqno from the error here','Put the same xact_seqno from the error here too' - for e.g. something like this:

EXEC sp_browsereplcmds '0x0005554B00001F180001','0x0005554B00001F180001'

This will list all commands corresponding to that xact_seqno - in the results locate the "command" column for the apporpriate command_id in the error message...much like what you have already done - however it is strange that there are no parameters to the update SP called what you posted...

Normally you'd get some values for the update SP from which you can figure out what the PK of the row(s) in the table on the publisher that are not able to get updated on the subscriber and then get that data into the subscriber after which things should work fine