Unreliable USB ethernet Linux v5.1-rc3-bone0

Still working on getting a PocketBeagle(ish) board fully up.

This board is using an ST1633 touch screen and I need a very current kernel to support that.
So I jumped to v5.1-r3c-bone0 using the bb-kernel git repository to cross build.

I am having some minor problems with that as more than half the time ./build_deb.sh fails compiling the kernel.
But I can usually just run it again and most of the time it succeeds.

I am using a USB dm9601 ethernet NIC to connect to the board for debugging.
This is working fine with the 4.18.20-bone16 kernel.

But when I install the linux kernel deb for 5.1-rc3 the DM9601 is detected late in the boot, it is named eth0.
Ifconfig lists it as expected but it did not dhcp an address.
I can use

MAC=00e04c534458
connmanctl config ethernet_${MAC}_cable --ipv4 dhcp

to get it to dhcp an address,
but the change is not persistent accross boots and the connection does not stay up very long before dropping.

I can go to /boot/uEnv.txt and set
uname_r=4.18.20-bone16

reboot and everything works fine.

I have tired to look for linux .config file differences between 4.18.20 and 5.1-rc3 - there are alot of them.
I beleive I have picked up any that might have anything to do with this.
But still not joy.

Any Ideas on something else I can try ?