MC31 and MD4 system no longer updatable via ethernet

I have a system with an MC31 and a MD4. The major portion of the application runs on the MC31.

I used to be able to update the MD4 via ethernet, then it re-booted in some gateway mode and continued to update the MC31 acting as some ethernet to CAN bridge. This was a great feature. Since a while, maybe since 3.19, the firmware loads into the MD4 via ethernet, reboots and waits for the MC31 but nothing happens. I have waited many minutes and the update never completes. This is using the same hardware and wiring that used to work. Is this a know issue?

Also, maybe un-realated, I now have issues seeing values in debug mode when connected via ethernet, but everything is fine on CAN. Could the parker CAN link between the MC31 and MD4 be saturated? This would explain the bad debug performance as well as the reflash issues.