I have internet via coaxial cable (aka cable TV). The cable modem is of type Netgear CG3000. (comes from the ISP). The connection is of type DOCSIS 3.0.
About a year ago the cable TV guys went through my home and replaced cables and other components to be best-of-class with presumably no chance of interference. My installation is pretty simple. There's no amplifier (no need to according to the cable TV techies that have visited my house) and only a single splitter that splits the signal into data output and TV signal output. Everything installed by the cable company using best type of hw. We only have a one TV in the house.
Since the techies fixed my installation - and I paid for that - my internet-via-cable has been rock solid until a few weeks ago. Now the modem will frequently drop the connection to the ISP (as indicated by the status lights on the front). It will typically last for 1-2 hours. The connection will always restore itself at some point without me intervening. Power cycling the modem does not help. The outages only seem to be happening during day time, never during night time. My TV signal has always been crisp and clear and without outages. Only the Internet signal is affected.
I live in a single family house.
About a month ago the cable company announced that they would upgrade their infrastructure and turn up the speed for all their customers. This would all happen behind the scenes. Indeed I can see now that my speed has doubled (that is when I manage to get the modem to actually connect). This is the only thing I now of in my environment that has changed.
On my request the Cable company will send technician in a couple of days and I suspect we'll start from Adam and Eve again when he arrives.
What might the cause the problem? (assuming my in-house coaxial infra is stellar). I've heard that it is possible for neighbors with faulty devices to interfere with my signal. Could that be true?
UPDATE
For those who can interpret it here's the connection stats from my modem (when the connection is UP):

UPDATE 2
From reading this it seems to me the modem's reported power levels and signal-to-noise ratios (SNRs) are actually quite good (when it is UP). This suggests to me that the problem arises when something in the vicinity is turned on and then goes away the moment that something is turned off.