Terminal emulator slowdown

Here is a problem that I've had a tough time isolating.

We use point-of-sale software that connects to a Unix server and we use Multiview 2000 terminal emulator to connect. It's a simplified interface that is entirely keyboard-based. The problem is that some users experience latency when entering data. Basically they'll type a sku in, have to wait 5 seconds, then it will catch up with itself and appear. I'm attributing the slowdown to a background service running on their systems like updates but I can't pinpoint anything.

Basically I'm wondering if there is any monitoring software (preferably freeware ) that you guys can recommend that will monitor performance spikes and give me info such as the time they occured and what program was using lots of resources then.

I want to be able to have the user phone me, tell me when exactly a slowdown happened, and I can review the logs and get some answers.

I've had no luck so far so I'm hoping someone here has been in the same boat as me before. Thanks guys!