Have to double-press keys to type with NEO keyboard layout

I use the ergonomic NEO layout which has a special programming layer that can be activated by holding the Mod3 key ("capslock"). So, for example, Mod3+A (= Capslock+D on Qwerty) = {.

The problem is that in QtCreator, I always have to double press the key, otherwise the keystroke isn't registered.

It should work like this:

press Mod3
press A // should print {
release A 
release Mod3

But in QtCreator, this doesn't output anything. Instead, I have to do this:

press Mod3
press A // eaten
release A 
press A // prints {
release A 
release Mod3

Once the editor has registered that Mod3 is down, a single keystroke suffices (which makes it more annoying because it's not something you think about while typing):

press Mod3
press A // eaten
release A
press A // prints {
release A
press E // prints }
release E
release Mod3

The problem only occurs in the code editor. Normal text input fields are unaffected and work as expected. I also tried this in Kate and it suffers from this problem, so I assume it's using the same editor component (please let me know if I should report this somewhere else). Oh, and it only happens on Windows. On Linux there are no such problems.

Steps to reproduce

• Download and install the kbdneo driver.
  (See attachment 1-neoinstaller.png)
• Activate the new layout under Control Panel → Change keyboards or other input methods → Change keyboards → Add → German → Deutsch (Neo 2.0 ergonomisch)
  (See attachment 2-enable-neo.png)
• Type any layer 3 combination

For more information about the layout, please visit the website. You can view the individual layers by hovering over them ("Ebene 1" - "Ebene 6").