A different kind of RDP performance issue

[Tom3.14159]

I'm running VBox 5.2.10 on 64bit Ubuntu with current guest additions, although this problem has existed for many recent versions of VBox.

In my Win7 guest, I often use Windows RDP to connect to 1-3 Win10 VMs that live in the data center where I work.

My problem is that the guest performance is awful (the guest is often frozen - even the mouse won't move), but only while one of the RDP sessions is running a network-intensive or CPU-intensive Excel macro.

Here are some of my observations:

1) Oddly, guest performance tanks, even though the macro that is running in the data center is not trying to communicate with my guest VM.
2) All 3 RDP sessions can be open at the same time, and performance in the guest is normal, but only if none of the connections are running a macro.
3) It doesn't matter whether one RDP session is open, or all three. As soon as any one of them starts running a macro, performance in the guest tanks.
4) Thirty seconds after closing the RDP session that's running the macro, performance in the guest goes back to normal.
5) This happens with every macro, not just the ones that run complex SQL queries.

Any suggestions?

TIA

Tom

[Tom3.14159]

Since there have been no responses, should this be moved to a different board/forum?

[mpack]

Not necessarily, but a VM log would have been useful, per every other support discussion on this site.