Internet dropping out periodically

A few weeks ago, we moved into a new apartment. It's a renovation of an old building with no cable hookups, so we had to have Comcast rewire the apartment. They did that by drilling a hole through the outside wall and running the cable along the outside of the building. Since the same is true for all the other apartments, our cable was connected to a tangled web of splitters and long cables.

After we got our service activated, things seemed fine at first. Then we started to lose connection for hours at a time. Not slow connection, but completely off. The modem (motorola 7420) goes to a blinking green upload light, and a solid green download light, with the online light off. Our wifi network worked fine, but no internet connection. Power cycling the modem had no effect. On one call with Xfinity, the tech said she was getting bad power readings from our modem, suggesting it was somehow at the end of its life. We replaced it with a new one and still have the same issue.

Around this point we figured out that if we remove and replace the coax cable in the modem while we power cycle it, that immediately brings the connection back on. Not a terrible issue but we would like to not have to do that (eg it's always off when we get up in the morning, can't leave things going overnight).

Next we get a little reading online and came to the conclusion that the terrible web of splitters and cables outside was causing a power drop. At that time, our modem was reading around -9 dB. So we had a tech come out yesterday and he reconfigured that mess of cables so our apartment now connects directly to the street hook up, no splitters. At first we thought that made a big difference, because the modem readings went up from -9 to -6 to around 0 dB. But a few hours later we had the same issue. The connection just dropped. And again this morning.

Any ideas what could be causing this? Or what we (or hopefully Comcast!) can do about it? Calling the phone number and starting from scratch for the 7th time just doesn't feel likely to get us anywhere.