Question Latency Issues Driving Me Mad

[Anaphriel]

I've been with the same ISP for roughly a year now and hadn't had any issues until about 2-3 months ago when this problem first started.
Standard operation of my internet connection is pretty solid, it's only when I start to try online gaming that the issues begin to arise. 90% of the time, my connection will be fine, yet the other 10% (which is usually in some critical point of the game) my ping will skyrocket, I'll be locked in place for 5-6 seconds, and then it'll go back to normal.
During these times, I Alt+Ctrl+Del and go into task manager, and each time, the Networking tab and the tracker is off the charts...literally.
Troubleshooting I've done so far....

Called my ISP and they told me they could see a lot of interference on my connection. They sent out a tech, and he replaced the entire line from the phone pole to the demark, and from there to my modem.
(Didn't fix it)
Replaced my entire Modem
(Didn't fix it)
Replaced the ethernet cable
(Didn't fix it)
Updated all drivers, firmware, etc.
(You guessed it)

When I run a ping test to 8.8.8.8, everything comes back fine. Running Speed Test, everything is normal.

This affects both my Ethernet and WiFi connections, but in different ways. On WiFi (on my phone) certain messaging apps, like WhatsApp will hang for upwards of 10 minutes before sending or receiving anything, so I'm now forced to use my Data plan if having a conversation.

My WiFI is run on 5g, I use WiFi Analyzer to track the strength. On paper, and through programs used to monitor my online activity, everything should be fine...but it's not.

My ISP is basically just shrugging at me at this point and I have no idea how to fix it.

 

[failboat]

monitoring traffic is crucial in trouble shooting. it's also not a common feature on routers. if you're lucky you can see a graph of throughput over X time. if you're congested for 10mins it will show on a graph like that. if you have a spare pc with 2 nics you can run a fully featured router for free. you can test if you're being ddos with pfsense or ipfire. this is a very difficult check because the packets are dropped and not shown in logs.

when the isp comes and does a line test they test straight to modem on a wire. if you are able to play for a night like that try it. keep your FW on. you can use resource monitor in windows which is helpful if you're the only client. you will have to test with as little variables as possible to see if you get good results.

any type of download or upload can cause bufferbloat which kills your latency. it's designed to do this and the isp doesn't care as long as you get throughput it's not their problem.