That’s very weird.
We did a test with different routers like Linksys, Netgear, D-Link with factory and open source firmware’s on the router but we never seen that problem.
Are you saying you had that issue with both two router is that correct?
Could you please try to use different cable, or to connect directly to any computer does the problem is present in this case as well?
Sorry to ask that much question but you are the first user who has this issue and I’m not really sure what can cause any similar issue.