This year I have taken my crombro to each go so far this year to compare what it reads compared to the bfta chrono.
From memory and will change when I look at my records tomorrow as I made a note of the chrono number as well I hope.
GP1 I forgot to check the batteries and they were flat. Doh
GP2 mine 761 bfta 757
GP3 mine 777 bfta 785
GP4 mine 773 bfta 769
I had mine set up by John Ostler for 770 when serviced nearly 3 years ago and not touched it since and come Winter and Summer it is with +/- 10fps of what I expect.
If you can could you use your crombro and another type to compare results?
Life,e Neil I use one of the alignment tools for consistent placement.