Brakes do not work when taxiing over certain parts of tarmac?

[Moespeeds]

I haven't flown the hawk in a few months. I broke it out this week and have this strange problem where the brakes suddenly fail when taxiing over certain taxiways or parts of the tarmac. Once I slide off the asphalt and into the dirt, the brakes suddenly work again. This is repeatable in certain areas. Brake pressure shows ok. Same effect with experimental and regular flight model. Using unstable 11.5 beta.

Thoughts?

Thanks!