Is vomiting (not related to gagging) normal?

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DS is 8 months old. We started giving him solid foods at 6 months old and are doing BLW. He has breakfast, lunch and dinner, no snacks. He has a healthy, varied diet (a lot like ours but less alcohol and chocolate ).

Every 10 days or so he'll have a massive full-on vomiting episode in the afternoon, usually after waking up from a nap (a good few hours after lunch). TMI - it looks like milk and partially digested food.

It doesn't seem to follow any particular types of food. One day he'd had baked sweet potato with salad and another he'd had Welsh rarebit. He's usually a bit fussy beforehand and then fit as a fiddle afterwards.

He is breastfed and still feeds about 8 times a day. He has tracked 75th percentile from birth and is otherwise fit and well.

Is the occasional puke just a normal part of weaning or is this a bit odd?