So after more troubleshooting, they send out another technician.
He swings by and says that my area (Annandale, VA) has been having issues with the PON cards where they increment a bit error counter over time. As this counter gets high enough it starts causing issues with peoples' connections.
Apparently it happened last summer and they just reset the PON card which fixes the issue but is not a permanent solution as the PON card will just start incrementing more errors over time.
Each time the counter gets high enough and starts affecting enough households, the complaint/ticket call volume goes up and they reset the card. Errors go away and they considered it resolved as calls stop coming in.
And the cycle repeats itself ad nauseum.
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The tech was out here at like 7PM testing things out and mentioned all this to me.
Says he saw the slow speeds and issues I've been complaining about during his tests and eventually gets it to test fine and, of course, the CO says things are testing fine on their end as well and don't see anything wrong... Of course if you test it enough times you might get through one time at the correct throughput; that doesn't show consistentcy of performance at that speed...
So anyhow, since it's just me and not a high volume of people complaining they don't want to reset the PON card as it'll take the rest of the people offline for however long it takes to come back on.
He also mentioned that he hasn't been called out for any issues like this for people on GPON; only BPON. This again points towards it likely being an oversaturated BPON OLT or bad PON card.
The forum team asked me to contact them again when the speeds are lackluster so the NTs can take a look at the circuit while it occurs and likely it will be a different NT than the ones prior leading me back towards testing/troubleshooting the same things that have been proven not to be the problem.
Edit: This thread here has lots of similar information and is the likely culprit.