Do babies lose skill of putting themselves back to sleep?

Hello,

my son was sleep trained using a modified Ferber method (takingcarababies program). He slept well for several months. He is now 12 months old and may have gone through a ‘regression’ but I’m not sure. He now is breastfed back to sleep every time he wakes up through the night after trying to pat him back to sleep, rock him back to sleep, etc.

Does he need to be sleep trained again? Has he lost the skill of putting himself back to sleep independently following a wake up at night?

what do you suggest as next steps?