Gathering table statistics on primary impacting apply on logical standby

We have been hit with a issue where manually gathering stats on the primary database is slowing down the apply on the logical standby by a lag of almost 6 hours to catchup.

Due to some performance issue on our primary database we had been advised by our third party vendor to disable the scheduled nightly default gather stats job and manually gather stats on the application schema tables via their script which we are running via cron.

Ever since we are running the gather stats manually the logical standby lags behind and taken almost 6 hours to catchup after the gather stats job completes on primary.