@Kim he was sleeping in a bed side bassinet that rocks. (I think I messed up there 😂)
If he is still safe to sleep in the bassinet may want to use that again without it rocking since he is more used to that and once you get the longer stretches move to the crib. Or keep crib for nap time and bassinet for at night so he understands crib is safe too still
How was he sleeping before you transitioned to the crib?