Studio 50 Firmware Update via USB

Hello, 

I am attempting to update over 100 Poly Studio 50s via USB. They are all in MS Teams mode. 

If the Poly is on the screen the MS Teams welcome splash screen (the one where you press next 4 times), the Poly will recognize the USB update drive and update.

However if the Poly is waiting for a call, it will not recognize the USB drive. 

Is this normal behavior ? If so, is there a quick workaround to get back to the MS Teams splash screen without switching to POLY mode and back to TEAMs ? 

I'm trying to come up with a solution to update all these Polys as quickly as possible. 

Thanks !