Hydraulic brake - intermittently stops working altogether

Hi

The back brake on my new cx bike is doing weird things. Its works perfectly most of the time, then every so often just stops working altogether. This has happened three or four times recently and nearly caught me out badly on a big descent today. I thought it had something to do with the engaging the gears shifting instead of the brake by pushing the lever sideways before braking, but its definitely not that. I was pumping like crazy today and no sign of it working.

It comes back to life after usually after a few seconds. I've never had a similar issue on a mountain bike so a bit in the dark. The make is shimano hydraulic RS785. Suggestions welcome

Ronan
Flush out the fluid and re-bleed. Check for leaks at the calliper


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