Support for new Archer c5 v4

Hi, I'm new here and need help.
I've installed openwrt 19.07.2 to my Acher C5 v4 router (using tftp tp_recovery.bin from 192.168.0.66 method).
It doesn't work as expected (cannot save any setting) so I want to go back to the original fw.
Unfortunately neither the tftp recovery method with reset button nor the uart tftp recovery method work for me.
I have uart console acces, but none of the back_to_stock_firmware methode works.
With UART:

U-Boot 1.1.3 (Aug 15 2019 - 08:56:44)
MT7620 # tftp 0x80060000 tp_recovery.bin

 NetTxPacket = 0x83FE3FC0

 KSEG1ADDR(NetTxPacket) = 0xA3FE3FC0

 NetLoop,call eth_halt !

 NetLoop,call eth_init !
Trying Eth0 (10/100-M)

 Waitting for RX_DMA_BUSY status Start... done


 ETH_STATE_ACTIVE!!
TFTP from server 192.168.0.225; our IP address is 192.168.0.2
Filename 'tp_recovery.bin'.

 TIMEOUT_COUNT=10,Load address: 0x80060000
Loading: Got ARP REPLY, set server/gtwy eth addr (2c:fd:a1:1e:ff:a9)
Got it
T T T Got ARP REQUEST, return our IP
T T T T T T T
Retry count exceeded; starting again

With reset button:

starting recovery...
Read MAC Address from Flash
raspi_read: from:7df100 len:6


 NetTxPacket = 0x83FE3FC0

 KSEG1ADDR(NetTxPacket) = 0xA3FE3FC0

 NetLoop,call eth_halt !

 NetLoop,call eth_init !
Trying Eth0 (10/100-M)

 Waitting for RX_DMA_BUSY status Start... done


 ETH_STATE_ACTIVE!!
TFTP from server 192.168.0.66; our IP address is 192.168.0.2
Filename 'tp_recovery.bin'.

 TIMEOUT_COUNT=10,Load address: 0x81000000
Loading: Got ARP REPLY, set server/gtwy eth addr (2c:fd:a1:1e:ff:a9)
Got it
checksum bad
checksum bad
checksum bad
checksum bad
T checksum bad
checksum bad
checksum bad
checksum bad
checksum bad
checksum bad
checksum bad
T checksum bad
Got ARP REQUEST, return our IP
T Got ARP REQUEST, return our IP
T checksum bad
checksum bad
checksum bad
T T T T T T
Retry count exceeded; starting again