steveodsi :
if your usage is above than 350MB then use F5 load balancer.
Cisco 3850 will be the best router for your need.
A 3850 is not a router it is a layer 3 switch. It can not do nat like his tplink device can. It also does not contain any ability to configure any form of load balancing other that what you can do manually with routing. It has no ability to detect a path outage other than a simple port down. The lack of these feature is what differentiates a layer 3 switch from a actual router.
Sure a F5 will work but that is like recommending a private jet to the guy who is buy a economy seat on a plan. The tplink box he is using costs less than $75.
This sound like a bug in the firmware. The best first step will be to see if there is any newer firmware from the manufacture.