Different behavior

Hi! I would love to know if some of you have babies who will behave differently at home vs with grandparents/ other caregiver. My baby always slept pretty bad, we exclusively contact napped until 10 months old, lots of night wakes ups,etc. He's a very energic 14 mo now and he spends 2-3 days a week with his loving grandparents (we started this 6 months ago). There he sleeps independently in his cot, no peep or anything, always happy and content. My MIL even says she can't keep him up longer than 3-4 hours (we are trying to do 1 nap a day but it's impossible for her). At home he fights naps, he will stay up 4-5 hours no problem, and especially with me will not sleep independently at all. I have to lay with him for 30+ minutes until he falls asleep. For night sleep is hit or miss, sometimes he sleeps through, other times he's crying 3-4 times at night. With my husband he'll fall asleep faster. Why is this happening? It seems he's a different baby with other people. I've always been present, I would say we have a very good attachement and relationship.