Hi Glen,
I test it and it's like the reset command is not always recognized by the PB-Pro, this happen after a track call and also when you click on the "start race" button immediately just after the race end (to start the same race).
In fact it's like sometime the reset command have to be send two times to the PB-Pro, Pc Lap Counter send the reset command just after the race setting and also when you start the race but it's like this is not enough...while waiting for a solution here is a work around:
before starting a race always click on the "new race" button and accept the race setting screen ,normaly just after the race setting the PB Pro should display "9999", sometime it does not but when you will start the race the PB-Pro will always display "9999".