Infrequent UBoot issue

gistfile1.txt

GOOD:

ar7240> erase 0xbf040000 +0x160000
Erase Flash from 0xbf040000 to 0xbf19ffff in Bank # 1
First 0x40 last 0x19f sector size 0x1000
 400
Erased 352 sectors
ar7240> cp.b 0x81000000 0xbf040000 0x160000
Copy to Flash...
 Copy 1441792 byte to Flash... write addr: bf040000
done
ar7240> boot
## Booting image at bf040000 ...
   Image Name:   FreeBSD
   Created:      2019-05-20  18:56:56 UTC
   Image Type:   MIPS Linux Kernel Image (lzma compressed)
   Data Size:    1360999 Bytes =  1.3 MB
   Load Address: 80050000
   Entry Point:  80050100
   Verifying Checksum ... OK
   Uncompressing Kernel Image ... OK
No initrd
## Transferring control to Linux (at address 80050100) ...
## Giving linux memsize in bytes, 33554432

Starting kernel ...

CPU platform: Atheros AR7240 rev 2
CPU Frequency=400 MHz
CPU DDR Frequency=400 MHz
CPU AHB Frequency=200 MHz
platform frequency: 400 MHz
CPU reference clock: 5 MHz
CPU MDIO clock: 5 MHz
arguments:
  a0 = 00000007
  a1 = a1f71fb0
  a2 = a1f72460
  a3 = 00000004
Cmd line:argv is invalid
Environment:
....

BAD: 

TftpServer Timeout;
no file was loaded.
## Booting image at bf040000 ...
   Image Name:   FreeBSD
   Created:      2019-05-20  20:08:33 UTC
   Image Type:   MIPS Linux Kernel Image (lzma compressed)
   Data Size:    1153575 Bytes =  1.1 MB
   Load Address: 80050000
   Entry Point:  80050100
   Verifying Checksum ... OK
   Uncompressing Kernel Image ... OK
No initrd
## Transferring control to Linux (at address 80050100) ...
## Giving linux memsize in bytes, 33554432

Starting kernel ...