VPN device knocking other devices off splitter?

Hi,   I'm having a strange problem.   I have a Netgear splitter ethernet wire connected to the hard wired ethernet port of a comcast router.   I completely power cycle all devices and the splitter every night.   One of the devices is a VPN attached Win 10 machine for my work.   In the afternoon intermittently, another Win 10 machine on the splitter just drops its DNS setting and can't use the internet.   Rebooting the other Win 10 machine or moving the problem ethernet plug  to another splitter port doesn't fix anything.  Through all this the VPN work machine works like a champ.   I have this same problem of the DNS dropping with a Mac also.   Is it possible the VPN on the splitter is kicking other devices off the splitter?   When I power cycle everything overnight the splitter always works well for all devices the next morning.  I do have a Netgear Nighthawk router ethernet wired to the Comcast router and I didn't do anything special to make one the master or anything but the splitter is connected directly to the Xfinity router and doesn't go through the Nighthawk.