VVX310 - LAN/PC ports speed problem

Hi and welcome, as this is my first post here.

I'm having problems with VVX310 phones. Both have been upgraded to the latest version 5.7.2.1277 and been restored to factory settings.

Now, the thing is - I have two phones:

a) phone A, LAN port connected to unmanaged 1Gb/s switch port, negotiated speed is 1Gb/s

b) phone B, LAN port connected to unmanaged 1Gb/s switch port, negotiated speed is 100Mb/s

Both phones, if PC port is connected to either switch or PC (both devices can go up to 1Gb/s), they negotiate only 10Mb/s.

So there are two problems:

- LAN port speed for phone B

- PC port speed for both phones

The only difference is that phone A has "Rev K" written on the bottom sticker, and phone B - "Rev J".

Any suggestions?

Could those be a firmware issues?

Regards

Lukasz