DX Wombat
Dumping fuel wouldn't start a fire, it evaporates instantly. If there was already a fire crew wouldn't dump.
Looking at the altitude I am +ve engine was shutdown. 17,000 is well below single engine ceiling.
I think people are mistaking the flames coming out of engine as a running engine. That is probably just gushing fuel on fire. Flames on the flaps may be result of open jettison nozzles at the wing tip. Why they were still open, we don't know.