User's mouse stops working when sharing

This has happened to, at least, two Zoom calls with different users.  They are sharing their screen and mouse icon changes from a pointer.  At this point, it no longer works with whatever application they are showing me. The work around has been for me to force share my screen (their mouse d/n work).  They then get control of their mouse.  I stop my share and they share the screen again.  That usually lasts a few minutes and we have to repeat. 

I believe I am on the latest version of Zoom (auto update). I doubt they have the desktop version installed but I do. Any idea what setting needs to be changed here?