Different foreground value is applied to elements, which are present inside RadBusyIndicator when using the Office2019 theme.

To work this around, set a new value to the Foreground property of the RadBusyIndicator control.

Using the Fluent theme with a higher DPI, e.g. 125%, the spinner ellipses of the BusyIndicator appear cut off on the top and bottom when a higher DPI is used and the control is hosted in the DocumentHost of a RadDocking instance.

Missing biding to Foreground in the ContentPresenter of the control which prevents not styled controls (i.e. TextBlock) not to receive the proper Foreground for the current theme.

Workaround:

add Foreground = "{TemplateBinding Foreground}" to the ContentControl in the ControlTemplate for RadBusyIndicator.

Scheduled for: 
The fix for this issue will be available with LIB (version 2018.3.1203) published on Monday, 3-rd December, 2018. 
 

Available in LIB version 2016.3.1017, it will be also available in the 2016 R3 SP1 release. 

Available in LIB version 2015.2.810, it will be also available in the 2015 Q3.

If you change the Culture at run-time and reload the control, the new culture doesn't apply.

The title is accurate but the description is pretty far off. The problem is that a RadBusyIndicator with a DisplayAfter of 1.5 seconds and IsBusy=true  will initially set its contents to disabled and then enable the contents when IsBusy becomes false.  The

Available in LIB version 2015.3.1207,  it will be also available in the 2016 Q1 release.

please test again and add steps to reproduce