Why does the video drop during a conference call?

Such cases have already been reported many times. The fact that it is now happening with all three of your devices is very strange. Here is a brief overview of how this problem has been solved for other users:

Check cable

• Often the cause was a defective cable, which could be the reason if you used the same cable for all three devices.

Update firmware and software

• It has been reported that the Rally Plus often has black screen problems due to outdated firmware, especially with new devices from stock (they may be running on older versions).
• Download Logi Tune (free app from Logitech: logitech.com/en/software/logi-tune.html). Connect the Rally Plus to it and check for updates for the camera, speaker and mic. Install all available firmware updates - this has improved video stability for many users.

Other procedures (to try out)

• Temporarily disable features such as background blur, auto-framing or video effects, as these can put a strain on the Rally Plus. Set the resolution to 1080p@30fps (not higher to avoid overloading). These settings must be made in the conference software.

If all this does not help, you should call Logitech support as the devices have a 3-year warranty.