Flipside,
I think you unconsciously solved the problem. If a 3P gauge continuously sends event commands to e.g. the autopilot instead of when they are needed, this can cause the effect of incrementing headings by 10 instead of 1, since FS is struggling to keep up with the gauge's input alongside everything else.
Three ways out: use a different panel (which is what you did); or if you like the panel and want to continue using it, you can go through the panel.cfg, REMming out the gauges one by one until you find the gauge that's causing the problem (unlikely to be any of the default gauges) and replace it with another one. Or you can use the registered version of FSUIPC which fixes this 'control acceleration' issue.
