Ridiculous GPS inaccuracy on running track

Where you using the track running profile or the "road/default" running profile?

I was using track mode.  I revised my text accordingly. Even with road/default profile, 200 meter error is still a lot.  What I want to say is that the track profile was fine before the update.  The FW18.23 just ruined everything.

When you look at the GPS track on Garmin Connect, does it appear as expected? no weird kinks or whatever?

I have a track workout scheduled tomorrow, time-based intervals though. I will try to keep track of my distance visually and report back if that works.

I went back to Gamin Connect.  Yes, it showed 20 laps.  Now, here comes the problem.  Why 20 laps on a standard and certificated track become 7800m? 

Any risk you ran in a track # different from the one in the profile?

No, I do not think so.  We are at first track, the same as the one in the profile. 

Mine has been fine before and after 18.23. Only thing I can think of is maybe you took off before the GPS got a good lock. Does the GPS track look normal? Are the start and stop points correct?

My most recent track workout was the above last Friday. 20 laps. Auto laps based on position distance (400m) which it typically nails every lap on the line, sometimes half step early/late.

Check this image.  This is where the problem is.  The record routes are not consistent on satellite image.

Ha! That looks like Datong track. I'm here in Taipei as well. Anyway, that is problematic indeed. Were you in the same lane the whole time? Watch on left wrist? Track mode set to Lane 1 (assuming you were in lane 1). Maybe check the GPS settings for the Track Run mode.