Mediatek build help

[Roy Walker]

I was trying to get Openwrt support working on a TP-Link Festa F61 access
point and wrote the image to the wrong off-set.  Didn't realize until I
restarted and was getting this on boot:

U-Boot SPL 2018.09 (Jun 23 2023 - 11:14:20 +0800)
Trying to boot from NOR
Error: LZMA uncompression error: 1
Trying to boot from UART

Failed to load U-Boot image!
Entering emergency mode.
Please transmit a valid U-Boot image through this serial console.
The U-Boot image will be booted up directly, and not be written to flash.
Accepted mode is Ymoden-1K.
I built a new u-boot image from source for the mt7621, but can't get past
this:

Starting ymodem transfer. Press Ctrl+C to cancel.
Transferring u-boot-mt7621.bin...
100% 257 KB 8 KB/sec 00:00:31 1 Errors

(SOH)/258(STX)/0(CAN) packets, 5 retries
Loaded 263882 bytes

MT7621 stage1 code Dec 16 2019 17:45:55 (ASIC)

CPU=500000000 HZ BUS=166666666 HZ

Change MPLL source from XTAL to CR...
do MEMPLL setting..
MEMPLL Config : 0x11000000
3PLL mode + External loopback
=== XTAL-40Mhz === DDR-1200Mhz ===

Any help would be greatly appreciated.

TIA