Found the problem is related to this https://github.com/raspberrypi/linux/issues/1342
> **WARNING** "In normal circumstances there is NEVER a need to run rpi-update as it always gets you to the leading edge firmware and kernel and because that may be a testing version it could leave your RPi unbootable". https://www.raspberrypi.org/forums/viewtopic.php?p=916911#p916911
Even the [rpi-update](https://github.com/Hexxeh/rpi-update) documentation now warns "Even on Raspbian you should only use this with a good reason. This gets you the latest bleeding edge kernel/firmware."


Fixed it by "sudo rpi-update" and a reboot.