I've never experienced or heard of these bugs before. I have had other bugs
which only popped up when using other third party controls with custom
designers, but these have been traced and sorted. Obviously, I can't trace a
bug that I have never seen or can't reproduce.
Contact me via my site and I will send you a copy of the source if you want
it, but it is only available in VB. I put source on my site in both VB and
C#, but there would be too much code to maintain twice for TabControlEX and
that is the only reason that the source is not posted on the site.
There's nothing special going on in the designer though, that you can't see
in my 'TabControl using Custom Tabpages' example, other than adding two
tabpages to the control in its OnSetComponentDefaults() method.