when ever you use those rotating machines you always get that buildup. This is because the chocolate is starting to harden, JUST because you set the temp to 91 does not mean it will stay there, even at 91 it will start to harden because of the way chocolate sets you cannot hold it for a long time especially when the chocolate is mixing and exposed to the cooler air.
My suggestion is to get the little dipper (what is it a few pounds?) and have everything you need ready to dip etc. Anytime the chocolate starts to get thick I would pour that into some break up bar molds so it can be sold as break up in your candy case or pour it in a pan and add almonds to make almond bark.
If I recall ( and I havent used the little dipper in 20 years) if the chocolate even when its fresh and flowing still creeps up the side and goes up and over the bowl and makes a mess I recall just being there to keep it in the bowl as I use it. I also think what I did was cut a chunk out of the top of the scraper so that any chocolate creaping up will hit the cut hole before it goes to the top and out the bowl and lets that act as an overflow you see in a bathroom sink. It also allows some chocolate to pass to the back to mix with seed chocolate.