In the portion of my flight where I am approach the Initial Approach Fix, usually descending between 6000 to 3000 feet or so, and less than 250 knots,, prob in HDG hold and Level Change, autothrottle , I suddenly start getting a fluctuating speed, the speed jumps between,,say 240 and 270, the wind noise changes in sync, prob changing about every second. A bit lower the effect goes away as quickly as it started. It seems to be a bug of sorts. I am using ASE. Does this happen to anyone else?

It's how ASE updates weather by default. There are update locking and wind smoothing options within ASE that might wanna try.Good luck

OK thanks I will look into that. I thought I had it locked below 20k but will double check..