Good morning girls, was there a regression in development for the kids…

Good morning girls, was there a regression in development for the kids or I don't even know what we have. My son has been pooping exclusively on the toilet since 10 months. Everything was fine, he would ask. But the last week it's been a nightmare. He cries, struggles, hides from me and poops his pants. Already today I gave up when he sat on the toilet for 20 minutes singing songs, said he didn't want to poop and ran straight away and hid. ? I suspect that his grandmother scared him. He is afraid of her in principle, and she came into our bathroom while the baby was pooping. Since then, it's just chaos. Waiting now