Speed Drops at Night

Every night around 7pm to midnight or so (I'm in San Jose, CA), my gigabit internet service drops to speeds of like 3mbps.  It doesn't seem to be consistent at that speed, it fluctuates a lot, but it stays that low enought to make many devices not work (Alexa, streaming, etc.).

It was happening for a couple weeks then I tried to call them to actually speak to someone (which I find is close to impossible), it mentioned it needed to restart my modem due to maintenance that had been done in the area.  After that restart, it worked for the next week or so and now it is back to slow night speeds.  

To me this seems to be an issue with their node or something, but they want to send out a technician to my house.  I agreed with the assumption that the tech will most likely find nothing at my house and can escalate the issue.  

Any thoughts?

Thanks in advance,

Don