Simulator Fit Data Playback File and Simulate data stopped working.

I'm getting no callback to my callback function "GPSData()" with

Position.enableLocationEvents(Position.LOCATION_CONTINUOUS, method(:GPSData));

All works fine on the device, it's just the SDK simulator not playing ball.

It used  to work fine, and I have gone back to SDK 3.1.3 when I'm pretty sure it worked.

I previously was happily replaying FIT files, but it stopped working about a month ago.... maybe when I upgraded from High Sierra to Mojave 10.14.6???

[EDIT]

Cracked it!.

I am validating positionInfo.accuracy which is now returning 0 from Fit files and Simulated data.

Odd, but I can live with it.