kwin/wayland sending ctrl and alt modifier keys to input-leap when i press backspace

i am trying to track down a peculiar bug. i am using two laptops, side-by side, with one keyboard and mouse, with input-leap (the barrier fork) as a software kvm to both. laptop A, which is linux mint xfce running x11, has the keyboard and mouse attached to it. laptop B, my future production configuration, is running nixos and kde/wayland. i have on occasion, used other computers with this setup, such as windows 10, ubuntu, etc.

this setup works flawlessly, except when the kwin session has focus and i press the backspace key. i checked one of those keyboard testing sites, and two modifier keys are being activated when i press backspace. i have verified that this problem does not occur when i relaunch kde with an x11 session. this issue has been posted on the input-leap github, and after i ruled out input-leap as the issue, i am following up here.

the initial issue on the input-leap github: