Your first build link has no slowdown code neither friction setting, and the second build has either the slowdown code or friction set, is that it? If you already have a build that works as you want, I fail to see the problem.
Your actor is sliging because your ring bounds are slopes. If you simply move an actor against a slope, it will slide against it, that's expected. If you have a stop/slowdown code on the first build, it's not being triggered when you stop while moving against these slopes, or the interaction between your code and the slopes is launching your actor all around, so issues on that regard are on your movement code rather than physics settings.