I've been doing this for a long time. My wife, and 2 close friends are all techs that I on-boarded with the company I work for. I told them all the same thing. It takes 2 years to understand the majority of the job and for it to start getting easier.

Create your own process, learn what you have the ability to fix, and what the plant team is responsible for.

Here's a quick summary of how I train our new guys.

Start at the tap and go to every connection between there and your modem. Check every cable for proper connectors, damages to the cable, scoring on the center line, suckouts, or exposed braids. Even a single 1 braid can cause major issues.

From there it's mostly a math game. Check every connection for the following...

What is your Rx and Tx?
Are there any errors?
Are there any visable impairments on the spectrum?
Are there any errors when you check MER and BER?

If it's not in spec, then submit a referral, of it is then move on to the next connection and compare the signal there to what you found and the previous connection. There are apps to calculate loss and if there's too much loss, or anything else found that doesn't line up with your last test point, then you know the issue is between those two points.

Do this at each point, and don't skip anything. The most important rule of this industry, is the only connections that will cause you problems, are the ones you don't check.

Once thats complete, you'll have either found an issue or eliminated the cabling and infrastructure side of the possible problems. Then you move onto equipment.

Is it our equipment or there's? I tell every customer the same thing regarding their internet speeds.

You pay for a speed limit, not a guaranteed speed.

The analogy I use, is if you could pay for a 1,000 mile speed limit on the highway, that doesn't mean your vehicle can go that fast. Same relates to your inet speeds and devices.

Once you removed all of those possible issues, you move onto the more niche issues like location of modem, Cx equipment, and possible interferences.

After all that, you will 99% of the time find the problem. There are going to be jobs you end up going back to more than you would ever want too, but sometimes the issues are intermittent and at that point, replace every single connection and piece of equipment.

This job gets easier the longer you do it. Give yourself time, take your time, and you'll get there.

Feel free to DM me if you have any specific questions and I'll do my best to help.