My findings are:

1)Job on DBSTU server: Agent history clean up: distribution is failing.

From the Job error I figured out was Table [dbo].[MSmerge_history] on distribution was missing.

This is causing issue? I am not sure...

2)I did a test for small database, it works fine.

The REPL_snapshot, REPL_logreader and REPL_dist are running fine.