Hello everyone, I'm new here and want to share my experience with this so far. I'm not trying to steal the thread or beat a dead cat by any means.
With regards to OP's post I'm going through something similar. I'm toilet training a cat using the ringed seat system and have somewhat failed. He was doing pretty good using the toilet system, but only once in a while he marked a place in the house with urine. A month or so goes by and I had to go out of town for a week. When I came back I found he had urinated and poo'd on my bed, on my clothes, on my furniture, on his stuff... well you get the idea (I had someone stop by a few times so it wasn't everywhere all fresh but I still had to clean and finally throw away a lot of stuff). He was saying "you left me I'm mad". I get it. Short re-run and he was back on the toilet.
For the record this cat has shown me he can pee and poo in the toilet with or without me watching. I've completely taken the toilet kit off with him using it fine. Then he started using the tub to pee and toilet to poo. This went on for another almost 2 months. Not right, but at least he's keeping it in the bathroom. I went out of town again for a week and this time he didn't go everywhere in the house. I also had a better person watching this time. A couple of months go by and here we are. This morning he peed in the toilet while I was brushing my teeth right in front of him. The other day he poo'd in the toilet while I was brushing my teeth.
What I'm realizing now is that he likes the tub better. First the peeing, and now the pooing. He's starting to do both in it more often and the more I try to get him to the toilet, the more he looks at me with that look (eyes almost closed, ears perked back almost saying I know what you want- but I'm going to act like I don't hear or see you). I wouldn't have an issue with this but after he's done he's tracking it around the house- especially the urine. This is mostly because he urinates on the opposite side of the tub's drain, and therefor it runs and gets on his paws. He knows I don't him using the tub because he runs as soon I catch him in there.
Today after I come home he drops a load in there. I see paw marks in the tub from him trying to cover it up and marking the tub slightly.
I can't stand the idea that this guy is slowly contaminating what "was" my brand new carpet. He used the a covered litter box in the bathroom prior to all this but that wasn't a whole lot better because litter was being tracked everywhere and the bathroom was always a mess. I would see litter clunked in his claws and it just didn't seem like the overall best solution. I cleaned his business every morning. Once a week or so I cleaned it out completely. I tried the floor mat for litter thing but it didn't seem to solve the problem either. I picked this guy off the street and we have about a 6 month relationship going. He gives me obvious signs he likes me and trusts me and everything is pretty much peachy. Although I can't say I'm not getting second thoughts on this whole situation if we can't work this out.
My theories on this are:
The toilet is uncomfortable (he has to perch, hold, and use his muscles). Although the special seat provided should help remedy this.
The toilet doesn't flush unless I flush it therefor if I'm not there he can't get rid of it. (The tub isn't any better at this)
The toilet water sometimes splashes when being used.
He doesn't like to pee/poo in the same place.
The toilet isn't clean enough (I'm conscience of this and keep it clean).
He doesn't want to go where I go. (I remove his toilet seat though)
The tub is more private.
You can't slip standing in the tub.