Your phone supports the 2 main LTE frequencies, band 13 and band 4.  That is good.

It is an overloaded tower and it does happen like clockwork, because it is.  People come to work, go to lunch, commute just like clockwork.  Your trigger is the people in the area going to lunch, like clockwork, and using their smartphones all at once.  The network never fully recovers until the commute is done. 

You you are just used to living in Maine, and not to a huge concentrated population like Fairfax, VA area. I know areas in San Diego this same thing happens, and in LA, and in San Fran etc etc.