How to Change or Disable U-Boot Boot Interruption Key?

[msksrv]

Issue Description:
I am using Armbian 25.02.0 on Amlogic S905X3 (Bookworm, kernel 6.1.127). I have a Zigbee module connected to the UART, and upon boot, it sends the character "A", which interrupts the U-Boot boot process.

I need to either change the boot interruption key or completely disable the ability to stop U-Boot booting via UART input.

Issue with saveenv:
I tried using the saveenv command in U-Boot to save environment changes, but it does not work. This makes it difficult to apply persistent modifications to the U-Boot environment.

Question:
How can I modify or disable the boot interruption key in U-Boot? Is it possible to do this without rebuilding U-Boot?

Additional Information:

Image: Armbian_25.02.0_amlogic_s905x3_bookworm_6.1.127.img
Hardware: Amlogic S905X3
UART connection is used for Zigbee communication
saveenv does not work, so changes to environment variables are not persistent
Any advice would be greatly appreciated!