The startBristol script uses the value of the first -p flag on the jackd command line as the value of frames-per-period for the jackd ALSA back-end.
However, jackd also uses -p to set the maximum number of ports: the -p flag can thus appear twice on the jackd command line.
If maximum number of ports is set to a non-default value in QJackCtl, startBristol finds the wrong value for frames-per-period, and can thus fail to start with errors such as this:
Jack period count mismatch: try `bristol -jack -count 2048`)
You need to ensure that bristol uses the same period size
Bristol is exiting ungracefully, ^C or ^Z will help
I've attached a simple patch to startBristol.in, which makes this work for me by using the last rather than the first occurrence of -p on the jackd command line to find the frames-per-period which jackd was started with.