Same issue here, it's quite frustrating. Unfortunately, I have no idea where to even start an attempt at a fix. Can anyone confirm that this problem does not persist when using the 1Gbit NIC? Edit: Can confirm that on the 1G NIC it works just fine. As @Ammonia said, the driver for the 2.5G must be broken. This reminds me of the time that the driver was removed, @Igor probably remembers.
This has been a real pain the last few days. Glad I found this post. Fortunately there is the 1G port as a backup. 1. When is the fix coming? 2. And can it then be installt via the regular apt update & upgrade?