ML350G9 - Server2012R2 - intermittently loosing network

[McLion]

Hi

I have a ML350G9 with Server 2012 R2 that intermittently seems to lose network conncetion.
- Shared drives vanish on the clients
- Connections to SQL server (SAP) crash
- RDP session shows error
and everything reconnects after a few seconds.

It could be a coincidence, but i feel like it started last friday night when I applied the June Microsoft updates.

I cant find anything in all the logs or event viewer - I have no clue what happens here.

Anyone an idea?
Thanks, Franz