You may be having wireless range or saturation issues. I would recommend checking that.
There have not been any issues with Chromecast, WiFi printers, multiple computers or cloud drives.
When I installed an 8ch kit to test at my own home, I had Chromecast, Smart TV, PS4, 2 PCs, 1 WiFi printer, 3 phones, and 2 tablets using a dual band router, with guest network enabled. My 2.4, 5, and guest all had unique SSIDs.
The NVR doesn’t play nicely with switches, and if your phone is connected to a different access point from the one the cameras connect to, it may have difficulty adding the cameras, even if they are on the same local network.