using Caps-lock to change keyboard layout is conflicted by Onboard

I use two keyboard layouts which I switch between with Caps-Lock (on a physical keyboard).
When Onboard is running, including when running in the background with no onscreen keyboard shown, I get the following problem:
Instead of switching layouts imediately, it activates caps lock, dithers for a few seconds alternating between layouts, and then deactivates caps lock.

To reproduce,
* Add a new keyboard layout on Settings>Text Entry (e.g. Greek)
* Set the shortcut to change layouts (switch to next source) is Caps Lock
* Make sure Onboard is running and open.
* Press Caps Lock and watch what happens on both the onscreen keyboard and in the status bar indicator.

Cheers,