I was briefly a network admin way back in the early 2000s. Core ISPs were playing (often petty) games with BGP routes back then for various reasons (eg forcing sub-optimal routes via AS padding unless downstream ISPs paid up). For awhile it got bad after the Dotcom implosion and networks were trying to up revenue. I've been out of the core BGP game for so long, but it's interesting to see how some things never change.
For the longest time I could not stream YouTube on my Google fiber connection without constant buffering unless I ran my browser through a socks proxy to a server outside of the ISP network.
Some time a few years ago they got it figured out and it's no longer been an issue. I could not explain to the CSR in terms they understood what the problem was.
I always assumed it was some kind of mis-configuration...