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SD card high-speed/low-voltage mode can only be exited by powercycling. Pi 4s before rev 1.4 lack the power switch required to do this, so must resort to a global reset that turns off many things, including SDRAM. To ensure correct operation, the bootloader checks that the SD I/O voltage is the expected 3.3V, forcing a power cycle if it isn't. However, this doesn't take advantage of presence of the dedicated SD power switch, always forcing a global reset, a consequence of which can be the loss of SDRAM content - including any ramoops dump of the crash logs. Make the bootloader more SD_PWR_ON aware, only triggering a global reset if one isn't found. See: https://github.com/raspberrypi/linux/issues/5298
rpi-eeprom
This repository contains the scripts and pre-compiled binaries used to create the rpi-eeprom package which is used to update the Raspberry Pi 4 and Raspberry Pi 5 bootloaders EEPROM images.
Support
Please check the Raspberry Pi general discussion forum if you have a support question.
Reset to factory defaults
To reset the bootloader back to factory defaults use Raspberry Pi Imager to write an EEPROM update image to a spare SD card. Select Misc utility images under the Operating System tab.