Trace/map not refreshing when Follow and Rec. trace are enabled

[Giraut]

I have this weird problem on one computer: my user ticks "Follow" and "Rec. trace" and nothing happens. But if the user reloads the page, the trace appears but still does not refresh. So my user has to manually refresh the page regularly to get trace updates. The Traccar UI otherwise works fine with no errors.

This one user has a Windows 7 computer with a very recent Firefox, no antivirus in Windows and no add-ons in Firefox. All my other users have Linux machines with Firefox, or Android tablets with Firefox Mobile, and the trace gets refreshed automatically for them. So I'm thinking maybe it has something to do with Windows.

Does that problem ring a bell?

Another, totally unrelated thing: is it possible to get rid of the orange dots on a live recorded trace? My tracker sends frames every 15 seconds, so the orange dots tend to crowd the trace unless zooming in real close.

Thanks!