Missed keystrokes when alternating MODIFIER(KC) and KC in quick succession

[lenarrdo]

I have encountered the following problem after flashing RMK on an RP2040-Zero:

• On my main layer, I have bound two keys to produce the following two characters: < and >. In Vial, they correspond to the keycodes KC_NONUS_BSLASH and LSFT(KC_NONUS_BSLASH), respectively.
• When I try to quickly input them in succession, it appears that some of the inputs aren't registered at all. For example, inputting the string <>< almost always returns something like << or <>.

Below is a short clip showing the problem.

rmk-issue.mp4