Never...I had that same problem on a Brison 2.4...was running fine then started running craappy...I to charged the ign. battery ,swithced batterys instaled new plug and finally found it to be the sensor pickup gap was to wide...dont know how it changed but brisons are imbeded in plastic and maybe the heat or something. all i did was push on it and hold it there ...runs fine now...maybe your pick up sensor has changed, is loose...I have brand new BME44 on a Sig Extra 300xs ...waiting for the wx to break here in Mi...then its going in a Great Plains Pitts Special that I havent even started building yet..cant believe BME recomends 20 gals of fuel to break in the motor before switching to synthetic oil. Keep us posted on your progress....
Dont ya just love these problems? never something simple eh

Ron