Orbi RBR750, webpages and iPhone Apps don't load

I've been reading through several posts in this forum around this same issue, and have not had any luck fixing our at home network.  

We have the Orbi RBR750, and have the Netgear Nighthawk CM1100 DOCSIS 3.1 Cable Modem.  Orbi Firmware Version V3.2.16.6_1.4.4.

There are two sepearte issues:

1. while on our iphone and connected to the orbi wifi, some apps and some webpages just wont load.  the odd thing is that sometimes the same webpages/apps that dont load, will load just fine at other times.  

2.  while working form our windows laptop, the connection works perfect for the most part, however at times when you navigate to a new webpage, for a couple seconds you will get a "This site can't be reached", "example.com's server IP address could not be reached".  It will automatically go to the webpage after a couple of seconds.  

I'm not a very technical person, so if there is more information that might be helpful to troubleshoot, please advise.