You're leaning differently
I have this feeling that you are leaning the Rans differently than you lean your road bike. On a road bike, you have a very low balance when most of your weight is on the pedals. You can lean the bike over more and not have the wheels slide. But with the Rans, your weight distribution is much higher on the bike, and I don't think you can lean the bike as much.
I once read about road racing on uprights that if you lean your body, and keep the bicycle mostly upright, you will slide the bicycle on some of those European stone streets, but it won't come out from under you.
So my suggestion would be to practice a different way of turning. Lean your body, but keep the bicycle as upright as possible while turning the front wheel. This will change the weight distribution, and may induce a skid without having the bike slide out from under you.
I opted for a LWB Rans Stratus, and have used this technique for my turns in it. Try this, and let me know how it works.