RAX200 Router having problem mostly isolated to 2.4 GHz

I purchased the RAX200 thinking it would have the best technology with the least problems; however, I was wrong.  

I have been having problems where my router will drop the most connected devices. 

I turned off smart connect, each of the bands is a different name, and all devices have been added manually. 
I have done some factory resets and take other recommendations by removing special characters from (which caused me to add each device again).  

Same issue with MU-MIMO on and off.  I have had the router replaced with a brand new one from Amazon once with the same problem.

I will say that about 70% of the time, there is an issue; all of the 2.4 GHz devices will get kicked off and not be able to connect.
30% of the time, it will just only allow 15-28 devices to connect.  When this happens, the prevention of connection is not isolated to 2.4 GHz but affects both 5 GHz and Ethernet as well. 

I don't know what to do I have been called back to Active Service with the COIVD-19 response and need this fixed for the family because I won't be around to troubleshoot and do band-aid fixes. 

My only thought is something is kicking the devices off; then there is a chaos of competition for IP addresses upon return.  But that would also not explain the isolation to 2.4GHz at times. 

Typically the go-to quick fix is reinstalling the firmware anywhere from 1-4 times before it works and lets all the devices connect.