Border caption with a bug?

I have a frameset with a frame in it, which shows a border caption (and an arrow). When I open this frameset to a new window, everything is fine, border caption and arrow appears.

Used formula:

@Command([OpenFrameset]; “CustomWelcome”)

When I try to open this frameset to another frame, then border caption is lost. Solely the arrow appears!

Used formula:

@SetTargetFrame(“WelcomeContent”);

@Command([OpenFrameset]; “CustomWelcome”)

Is this a bug and is there a workaround?