We researched this issue and concluded that there is no straightforward way to resolve it on our side.
Our tests show that the issue only occurs when the SchedulerControl.OptionsBehavior.UseAsyncMode setting is in effect. When Scheduler Control runs layout calculations in worker threads, those threads use a non-modified copy of the current application skin. The way in which the skin is copied makes it impossible to account for skin patches.
If you use skin patches to customize Scheduler Control's appearance, please disable the SchedulerControl.OptionsBehavior.UseAsyncMode
setting.