Wow, that's a really obscure bug, but you're absolutely right. I can confirm the problem. The issue is with the native SciLexer.dll library. With the ScintillaNET 2.6 release we ship version 3.2.3 of SciLexer.dll. Looking through the Scintilla release history at http://www.scintilla.org/ScintillaHistory.html it looks like this problem got fixed in version 3.3.8. To verify that, I downloaded the most current version of the SciLexer.dll from the Scintilla website (version 3.3.9) and tested it and was able to confirm that this issue has been fixed in that version and I now get the UpdateUI event on Shift+Tab.
I'm pretty sure that we'll be upgrading the SciLexer.dll we ship with ScintillaNET to the latest and greatest version soon but until then you'll have to do as I did and swap out your SciLexer.dll with a newer one. You can get an x86 (32-bit) build of SciLexer.dll in the SciTE Windows package from the Scintilla website. If you need a 64-bit (x64) build of SciLexer.dll you might have to do it yourself.
Thanks,
Jacob
I'm pretty sure that we'll be upgrading the SciLexer.dll we ship with ScintillaNET to the latest and greatest version soon but until then you'll have to do as I did and swap out your SciLexer.dll with a newer one. You can get an x86 (32-bit) build of SciLexer.dll in the SciTE Windows package from the Scintilla website. If you need a 64-bit (x64) build of SciLexer.dll you might have to do it yourself.
Thanks,
Jacob