Same issue, my ISP:
xs4all
Netherlands
Amsterdam

It seems that one of SE's peering partners has issues. SE should acknowledge the problem and talk to their peering partners why they have issues.
I am hoping SE is multi-homed and has multiple peering partners so SE they can route around bad peering partners.

The EVE Online datacenter is multi-homed for that exact reason, and they have routed around peering partners who fail. In fact they are now using an auto-routing system that detects routing failures for customers and can automatically find better routes for them.