CDC ethernet gadget: complete system freeze

We have an embedded T1042 NXP CDC ethernet gadget which seems to completely freeze when an
usb0 I/F is established and one do 1 of two things:
 1) reboot the connected Linux laptop -> CDC gadget appears to enter complete system freeze.
 2) on laptop, ifconfig usb0 down; rmmod cdc_ether -> CDC gaget freezes

I cannot finns and OOPS or other trace in console or syslog. I could really use som ideas here.
Linux kernel 4.19.108 (4.19.76 has the same issue)

 Jocke