I was going nuts trying to trouble shoot this ...A full day with the best avionics shop at KSAC doing software updates,re calibrating magnetometer,replacing g500 ahrs unit with another to rule out,inspected wiring,connector pins...etc...no change...My garmin g500 has functioned perfectly for 8 years.than all of a sudden I get the attitude display red Xing out.Always on the ground..on off on off...does it every time while taxing than snaps back on while on take off roll.Acts normal in flight..of