The tap dance stuff in the Moonlander/ZSA keyboards is really powerful. If you try to use two in one combo, though, one of the emitted key signals often gets stuck.
I had a key mapped to PgDn on tap and End on long press and another to backspace on tap and ctrl on long press. When I tried ctrl+PgDn, ctrl would get stuck down. My best guess is that a key up event that ctrl was waiting for got taken off the queue by the End long press listener. But that seems...too dumb? Why would it not notice what key is being released? There must be something else happening.