No boot-loader input on JTAG serial device

I'm trying to flash an MT7620 device running Uboot 5.0 and have JTAG access but can't access the boot-loader option during the UBoot process. Input is fine post boot. Could this be by design? I have another (identical) device with a different UBoot version and boot-loader input is fine on that one.


Quick bump. Anyone ever experience this?