Thanks for trying to help.
I am using Beeks VPS silver package (2700 MB RAM / 2 CPU / 50 GB Disk), and tried only running 2 Zorro instances directly connected to Oanda.
I had some troubles in the past 2 months (exceeding request rate limit), so I stopped running Zorro and VPS for 2 months. I just freshly re-started running Zorro this month with this new version 1.88 where rate can be adjusted.
So, probably, I don't think it is my VPS nor updating Windows issue. Anyway, I will try restarting everything if nothing else can be done.

Thank you.