Audio dropping in and out

I am an online therapist. Sometimes when I am on Zoom with clients and I play music, they describe my microphone dropping in and out. I have a run a full diagnostic check on my equipment and all is fine. It isn't a WiFi problem because they can hear the music perfectly. My headset is cabled and so it isn't a bluetooth issue. I'm beginning to think that this may be to do with the settings on their computer. However, unless I know what is causing this, I cannot inform them of how to rectify the problem. Any ideas? Please help!!!!