If, for any reason. the platform has developed a tilt (real or 'electronic' in the case of strap-down systems) away from true vertical. the accelerometers may detect such a tilt as an acceleration and integrate this to produce a groundspeed. Any 'residual' outside stated tolerances might indicate a platform problem. The highest I have seen is on a 737-300 on arrival on stand - 118kts - and, no, I am not prone to taxying on at that speed
. This was caused by the fitment of a non-approved IRS platform by the previous lessor.