JS Errors after upgrading from 5.3.1 to 5.4.3 and subsequent downgrade

2667v3 x2
32GB
1607 (14393.2848)

Timeline:
Using 5.3.1 fine, produced a video yesterday. Then decided to upgrade to see if there were any nice changes for a more important video I wanted to make next
Try to sync GPX and video - crash
Uninstall and reinstall - crash
Check firewall etc
Uninstall, wipe all directories related to Virb, reinstall 3.1
Still crashes

Issue is with this script which is fetched from your CDN
static.garmincdn.com/.../Track.js

function
SetTrackSegmentImpl( aLatList, aLngList )
{
if( !mTrack )
{
return;
}

***var theLats = $.parseJSON( aLatList );

*** is the reported error location, what it believes to be a syntax error.

A clean install on a W10 box works ok but I really need to get this going again on the workstation rig. If there was a simple way to purge and reinstall 5.3.1 would be great.

Cheers,
RC.