Canal Towpaths, cobbles and tyre grip

[Hell27]

I've been experimenting with different routes in this week, as it occurred to me that my normal road commute of 6.8 miles can be extended to about 9 using the local cycle route, which has a lot of off road sections. It makes it more fun and removes cars from the equation. As I've recently bought a CX bike it makes sense. So off I go on Monday morning, 1/2 a mile in and the bike went under me with no warning. The surface was wet cobbles. Checked the bike carefully, and the frame was crack free, but the right shifter was slightly bent. Ok to carry on though, and I had no injuries either. Got the bike fixed at Evans as its under the 6 week check. So, the next day I tried the same route on my mtb. This time also added canal towpaths through Manchester city centre to the route. It worked well, and the journey was epic fun even if I was completely covered in mud when I got in!
Tried going home today on the towpaths and on the CX bike but I felt the back wheel spinning out on me. Remembering Monday's off I decided to sod that and get back on the road. The surface felt like wet York stone, or Teflon as it felt like! Just wondering if my fellow CX commuters have experienced the same issues on canals and cobbles? The tyres on the CX are clement pdx 700 x 33 nobblies. On the mtb, I'm running shwalbe Hans Dampfs on a 650b, and the grip was great on all surfaces.