That happens when you plug the USB connector slowly. You don't believe it happens, do you? Just try various speeds of plugging!
Q: Can I use Sparkfun Pro Micro RP2040 as a drop-in replacement instead of a Pro Micro without having to modify the CRKBD PCB?
Yes you can! However, note that exising LEDs on your CRKBD may not blink RGBLED feature is still not implemented on PRK. And don't expect your existing CRKBS's LEDs will blink even if the feature is ready because the logic voltage of RP2040 is 3.3V while 5V on "normal Pro Micro". It depends on the specificaion of LED.
In terms of 3.3V, you should be very careful of the same thing which is warned on Proton C: https://qmk.fm/proton-c/
Some of the PCBs compatible with Pro Micro have VCC (3.3V) and RAW (5V) pins connected (shorted) on the pcb. Using the Proton C will short 5V power from USB and regulated 3.3V which is connected directly to the MCU. Shorting those pins may damage the MCU on the Proton C.
So far, it appears that this is only an issue on the Gherkin PCBs, but other PCBs may be affected in this way.
In this case, you may want to not hook up the RAW pin at all.
We saw some cases where the RP2040 broke due to a circuit that shorts RAW and VCC. HelixPico is another example.
The data in the flash ROM of RP2040 occasionally breaks for some reason. This is not a specific issue of PRK Firmware. It seems to happen commonly (and unexpectedly) on RP2040.
To fix it, download flash_nuke.uf2 from the following page and install it in "RPI-RP2" drive (not "PRK DRIVE" drive).
After installing flash_nuke.uf2, it will automatically initialize the flash ROM and possibly solves your problem.
Q: The newest release of PRK Firmware no longer works well while it seems to boot successfully, why?
PRK Firmware might get a breaking change. Take a good look at CHANGELOG.md