Hey, sorry that you're having issues. Here are a couple of things I would try:
1. Try to narrow down the specific plugin that is causing the issue. Test the Core plugin on its own. If that works, then test any of the plugins that may have an effect on keybindings or common events.
2. Test with a blank project
3. Disable the VisuStella plugins, add a new common event hotkey, then reenable the VisuStella plugins. Does the new common event hotkey work?
To pinpoint the exact problem, I would need access to VisuStella's code. Unfortunately, VisuStella's code is obfuscated (jumbled up) to prevent theft, so it's impossible for me to read it. If you haven't already, I would try contacting VisuStella Team first. My plugin is open source, so it would be easier for them to diagnose your problem.
Otherwise, you could send me your RPG Maker project and I could run some tests. You would still have to ask permission from VisuStella, since this would be tantamount to sending me their paid stuff.