Okay, here's what's happening.

1. PICO-8 open, playing a game.
2. We pause the game (with the Enter key) to go do something away from the computer.
3. We lock the computer with a key combination (Super+L) - meaning that PICO-8 was the active window before the screen was locked.
4. We return and type our password on the KDE Plasma lockscreen and hit Enter to enter it.

What we expect: the computer unlocks, PICO-8 is as it was before, paused.

What we usually see: the computer unlocks and simultaneously PICO-8 unpauses.

Just to check, we did the same series of steps with this text entry box in Firefox and Firefox does not register an Enter key press, so I'm guessing this is a weird edge case in how PICO-8 determines if the Enter key has been pressed.

In case the specifics are relevant, we are using Plasma 6 on NixOS 24.05 (Uakari).

Can confirm I see the same thing on Plasma 6.0.5 on the latest Manjaro.