About Potty Training a Special Needs Child

So my experiences this weekend reminded me of a time many many years ago.
Our family went on a camping/fishing trip and my baby bro came back from the trip
being scared to sit on the toilet and he also started stuttering. We (mom dad and I) found out later that older brother had went in the bathroom the outhouse kind of scary shit kind of bathrooms that only exist in the camping world unless of course you have to resort to finding a bush in the forest to relieve yourself upon and he told brother that he was going to fall down the abyss baby bro constipated for quite some time after we returned from the camping trip and if memory serves me correct it took him at least a week before he sat on a real toilet seat again.
So we flash forward to this weekend with my wonderful loving 99% of the time grandbaby Olivia. I've been knowing some time that she is a child with special needs and how to deal with that but now realize it really isn't any different than dealing with your other children or grankids...the trick is how to figure out how to best help them when they need you the most. Olivia did a great job with her potty training and now has resulted into pooping and peeing in her panties and then tells you much later that she needs them changed. Last night laying in bed --she likes to lay on grandma's belly and she turns over and I am patting her on the butt and feel #turdcity I'm like Let's go get cleaned up and she is yelling and screaming NO!!!. This is a child who last weekend spent with us was watching me on the toilet giving me high fives wanting to help me wipe but I was all "Nope that's not necessary LOL "and we both got "stickers" for being big girls who went on the potty . Suddenly she has turned into a child who pees or poops all over herself and has no concern about preventing that because she suddenly seems scared and doesn't want to do it anymore. And Olivia is suddenly screaming and crying and terrified about sitting on the toilet and she's pretty adamant about things she will or will not do without putting up a fight
So what do we do? Go with the flow? certainly we don't put her back in diapers. I've seen all of these posts about how sudden changes like a new baby or something significant in their life creates these kind of things but nothing new that hasn't been happening for quite some time now at least on our end. I'm basically at a loss about learning how to conquer whatever fears have now caused this set back. Chloe told me she thinks it is because they ran out of candy at her house and stopped giving it to her for a reward. I don't think the answer is that simple. But my thoughts will forever be that a special needs child's thoughts are way more complicated than simply being simple.
And more thoughts. That camping trip many many years ago when my younger bro became a temporary stutterer. It happened because he suddenly became terrified of something. The older bro should have never done that to him. But in retrospect the older bro always loved him. So there's that. And the younger bro was never a special needs child but for some reason became terrified about sitting on the toilet. How fucked up is that? When relieving yourself becomes your worst nightmare? Personally I have never had to deal with that but have dealt with people in my life who are terrified about simple things like sitting on a toilet seat. And am wondering if it starts with that and then carries over into your adult hood? And maybe if we are able to fix whatever is wrong it will not carry over? Jheez louise. Life is hard enough without having to worry about sitting on a toilet seat and being afraid of falling into the abyss. #JMO