I had a very minor frontal bump and ever since I keep getting front assist sensor impaired whenever I get to around 60mph , about a minute after this I get front assist unavailable. Also on the odd occasion the answer will kick in and scare the bejesus out of me . I’ve tried cleaning the sensor but it didn’t help. My mechanic says the slam panel has broken , could that be causing the issue ?

Do I need recalibration

If your mechanic means that the mounting bracket for the front radar sensor has been displaced or broken in the 'bump' it will require replacement and the radar will almost certainly need to be recalibrated.