By simply saying "The scheduler is hidden / does not work / something else in this / that browser", you are not providing us with enough information to simulate the issue locally and find the reasons for it.
The proper way is filing a ticket in our support system with a sample project that ALWAYS reproduces the issue. If there is anything specific to the issue, say certain steps to be taken, do outline those as well.
Without that vital information, we will be shooting in the dark and the chances of solving the issues are almost none.
In addition, are there any styles loaded on the page; is there is other JS logic present; what browser dies this happen in; does it happen only in a certain browser; what operating system is this; is it a real OS, or is it a virtual machine / virtualized one...
All those are the details that actually point us in the right direction where to look for the issues; ultimately they enable us to find, analyze and fix them.
If I am to make a wild guess is that while the schedulers are in the tabs, an event does not fire properly. Upon resizing the window, another event is thrown (most likely repaint) that shows the scheduler. But like I said -- that's just a guess.
All the best,
the Telerik team
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