Any top-level events which are not triggered (don't have a small green arrow on the left) are running on every tick.
Even with functions you still need to use that CPU_is_busy boolean flag. Set it to true inside the "LockUI" function. Set it to false inside the "UnlockUI" function. Check for this flag in different events. Add browser-log messages to events where you call "UnlockUI", to see which event has unlocked the UI.
I can't answer your questions about event 236 because it's not on your screenshots.
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Deactivating event groups when UI is locked is a good idea. For example, you can have a group with all keyboard shortcuts. Instead of adding boolean check to each event, simply deactivate the entire group.
To easily block all mouse activity I used this trick - place a huge TextBox with transparent background covering everything on the screen. It will intercept and block all mouse clicks, wheel events etc. In "UnlockUI" function destroy this TextBox.