Audio cutting out for musical instruments

I run a music school in Lagos, Nigeria and we teach clients across the world on zoom. Since the most recent zoom upgrade, we have been experiencing a serious degredation of audio with regards to instruments that is threatening the viability of our online lessons. 

We can hear the speech of our students very clearly but the minute they start to play on their instrument,  there is no sound at all. It's like the sound settings are optimised for speech and not for instruments. We have tried adjusting the settings on both our end and the students end so we are not compressing background noise and original sound for musicians is on, to no avail.  In fact, switching on original sound appears to make things worse.

Weirdly, this issue only seems to afflict laptops but not mobile devices. 

In my most recent class last night,  In my most recent class last night, BOTH my student and I had to connect our mobile phones to the call AS WELL as our laptops and use the mobile for audio.  Without that, she could not hear my piano, and I could no hear hers. 

Anyone else experiencing this issue and how are you dealing with it?