I have the N450/CG30000Dv2 Modem and I keep having issues with my internet speeds

I have the same unit and my speeds are 63Mbps down and 8.2Mbps up, I have everything set at stock settings. the only thing i'm seeing in my event viewer is a constant string of errors saying my computer has lost the lease to it's IP address DHCPv6 Client events, probably 50 per day (every 7 minutes). i just added a zero onto my keep lease setting on line it was set to 360 seconds now it's set to 3600 second but that's still only 60 minutes, (It should be able to go 3 days or so). Maybe 600 minutes or 6000 minutes 10 hours or 100 hours, that;s still only a little over 4 days. it was dropping the lease every 6 minutes I guess, My old router never had this error pop up even 1 time to if it still does it I'll add another zero and see what happens. I would check your Events and see what has been registered for you connection. Every time it looses or has a problem it will be recorded. I'll be your having a similar issue. I never noticed much of a slow down though.