Sites not loading / working correctly (Gigabit internet)

[connor.ebarratt]

For the past few days I have had an issue where many sites take a long time to load or will fail to load all the images / features on the page, While other devices on the same network encounter no problems at all. As an example gmail wont load all the icon images or netflix / youtube / imgur / facebook will take forever to buffer, where as ebay, steam, twitter and all others run fine.

NOTE: This is happening on all browsers
I am running on a gigabit connection with a router capable of handling. And I am using a wired connection. (I am getting correct speeds on speedtest.net, and downloading off steam confirms the correct speed)

I have tried the following:
Turning off and on the router
Set my computer to the highest priority on the router
Testing the cable on another device
Changing ip and DNS (Tried google and cloudflare)
Running a virus scan with Malwarebytes
Going to Microsoft
Calling my ISP
Cleaning my computer
Resetting windows completely
Making sure there is no proxy on

I have googled for days on how to fix the problem with no success.

Just in case here are my specs:
CPU: I5-6600k
GPU: Gtx 960
MoBo: Asus z170-ar
Ram: 8gb DDR4

Example:

 

[camieabz]

Have you tried disabling any PC-specific firewalls / AV / browser(s) ad blockers? You may have tested in several browsers, but may be running some common security across them all. Also consider the hosts file.

It might be that some cloud-based service or URL is stalling on your system. Something common to all the affected sites. By stalling, I primarily mean getting blocked.

Assuming you don't have specific router rules for your system, I would take the local network out of the equation. Renewing the PC's DNS cache and DHCP address (if applicable) can't hurt either. Perhaps take a look at any background services or processes that might affect such things. For instance when I was logged out of Google (ergo Youtube), I was getting strange layout and so on, and it took me a few minutes to catch on to why Youtube was 'misbehaving'. Logged into Google, and Youtube was back to how I liked it. Did you change anything prior to these issues?