We are doing end user blinkup after blessing, but the Imp001 doing the task seems to have stopped doing it correctly. In your experience do the attached blinkup have problems (apart form clipping)?
Turns out setting the speed to half in the EI delivered code example for blinkup, made it work.
The recommended way to send blinkup from a device would be to use the ffdac() peripheral to guarantee accurate timing. This can output on two pins of the imp001, and can be set to 142Hz for fast blinkup.