Disconnects/Timeouts with new line

Good Morning,

I hope you're doing well. 

Saturday morning, I woke up to having no internet. My neighbor was having their fence repaired and long story short, they cut my internet cable.
Sunday, I had a Xfinity tech come out to install a new cable, they did, and it brought my internet back.

Only problem is, since then, every couple of hours, my internet disconnects for 5 seconds and then reconnects. 

I can already see down the rabbit hole. I think support is going to keep telling me things I can do with my gear/on my end... when that is clearly not the issue.

Is there any support agent(s) out there who have seen a situation similar to this that might have a suggestion/solution? I'm looking for some sort of phrase I could say to a tech to have them quickly realize the problem.

- It CANNOT be my setup, my internet was perfect up until the cable was cut Saturday. The only thing that was changed was the new cable line. I'll be appreciative of any suggestions, but any suggestions about my setup I am going to ignore. I have not changed any of my software/hardware, the only things different are the dig job and the new cable.

Having said that, what can a tech do to hopefully remedy the timeouts/disconnects?

Do new lines sometimes have issues the first day they're installed until the network switch at Xfinity's hub is able to process the data? This sounds far-fetched.

Is there a possibility the crew damaged/cut more wires than just mine? How do I ask a tech to check that? They were only worried about confirming the cable from the cable box to my house was good. What about the cable that feeds the box from wherever it's supposed to come from?

Is there a noise issue somehow with the new line? Could a tech come out and install a splitter of some sort? Can someone remotely check that information before a tech comes out?

Maybe the location they installed the new line in the junction box (not the box that connects to my home, the box that is out in my neighbor's yard) is dysfunctional? Is that possible if the old line was fine? Is a tech going to know how to check that? 

Any info or suggestions would be appreciated. I could call a tech back out, but if they don't have any clue, it'd be a waste of money.
(I'm opting to pay for this myself instead of going to war with my neighbor.)

Thank you for your time,