Troubleshooting hysterical baby after visiting grandparents

My baby is 4 months old. My in laws are very active and present in his life. They’re amazing. They come to our place for quick visits, take him on walks and once or twice a week they’ll babysit him for 3-4 hours. He lights up when he see’s them.

In the last month however, there have now been 4 instances of him having an absolute meltdown either at their house, or as soon as he comes home from their house. They’ve brought him home early twice because they couldn’t calm him. Last night was the second time he’s done it at home and I cant calm him either. He is normally a pretty chill and easy baby, and an easy baby to put to sleep so its really out of character.

I thought maybe it had something to do with his routine being out of whack. They watched him last night so we could have valentines dinner. I wrote down a schedule and they followed it. He had been in a great mood. He got home about 9.45pm. It all went to crap when we tried to go to bed at 10pm.

He starts screaming out of nowhere. I mean the serious hysterical cry. I’m doing everything, all the positions, all the things he likes that normally work and he is still hysterical. He fights a bottle although he does take it and stops crying long enough to drink. He’s falling asleep so i try to put him down, he starts screaming. He finally falls asleep on my shoulder. I try to put him down after 20 mins or so, he screams. He eventually falls asleep on my shoulder again, i’m guessing around 11.30, i also fall asleep sitting up because i wake up and its 1.15am. I try to put him down, he wakes and screams. I give him another bottle. Theres more screaming. Its 2.30 when he finally stays down and asleep.

Its not that he would only sleep if i was holding him, its that he won’t stop hysterically crying. He falls asleep from absolute exhaustion from hours of wailing but the slightest movement, and certainly attempt to put him down, and he starts screaming again, as if he’d never stopped. He’s red faced, super hot, tears and snot running down his face and he’s so worked up and i can’t help him. I feel so terrible for him.

This only happens at or after being at my in laws. Any ideas why? Its easy to say ‘just don’t go to in laws’ but i just can’t do that. FIL is disabled and MIL works her butt off and the only time she has is evenings. They take my SIL’s baby a couple of times a week also. They love taking the grand kids. It was also a massive help to me in the beginning because it was often the only time i had to myself. My parents were less than stellar and my mum will never be allowed to be with him unsupervised so these amazing grandparents are essentially the only ones he has. He’s lucky to have them. I really don’t want to restrict anything between them, but we cant keep having this situation.

He had his normal naps during the day and last night they followed his normal schedule re awake time, feeds and bed time.

Why is this happening? What would you do?