Hi guys, hope everyone is doing great.
Let me start by explaining my setup, i have a sagemcom modem/router combo given to me by my isp and it simply has a poor wifi and its not just the rage but also transfer speed and connectivity. I have a few desktop, laptops and media streaming devices at my place and i would transfer files among them and with sagemcom i would get 1Mbs at average, to rectify this issue i put a tp link c20 router on dmz with the sagemcom modem/router and effectivly use c20 as the primary router and it solved my problem, now i can get 7-10 Mbs transfer depending on the type of file. Everything(internet connectivity, dhcp) works fine through the c20.

Now the problem i am currently facing:
This only happens when i am connected through the c20, whether its ethernet or wifi same issue. I would go to a website and it would start loading but would be stuck at a blank page and not be loading any content, then i would reload the page and it would load perfectly normal. This happens very rarely that i cant replicate at will.
Two websites it would almost always happen at, 1st is visa payment gateways( usually at 3d verification), same thing, it would get stuck and wont load the page then i would reload and it would work and other times transactions would fail and i would have to do the whole transaction all over again. Due to the nature of this process i cant replicate it again and again but as far as i can recall it happened every time i was making a payment and was connected through c20. 2nd is Wikipedia, it wont open at all(even if i reload the page), when i am connected through c20 router, android or windows same result but at the same time if i connect through sagemcom it would loadup just fine. I ran windows diagnostics on wikipedia and it detected that site was online but was not responding at ***port.

What i have done already and wiki still didnt load:
reset to default, took it off dmz, played around with dns(was already on google dns), even put isp given dns from sagemcom