Interesting. The voice in the video is mid countdown when it happens ("Ten, Nine....expletive") which implies the Super Draco engines hadn't fired yet.
If it's something like a pressure issue, it could be similar to what happened to AMOS-6, where there was buckled liner in a COPV [1] tank that caused a liquid oxygen buildup [2]
Someone on reddit captured the frames before and after, it looks like it's originating from just near one of the Super Dracos [3].
AMOS-6 suffered from a problem with a Helium Composite over-wrapped pressured vessel (COPV) that most likely had a liquid oxygen intrusion into the composite layer which due to the cold temperature of the helium created oxygen ice that violently reacted with the composite when friction ignited the combination. (Fun fact: as far as I know a liquid-oxygen drenched cigarette basically explodes when lit).
Afaik there is no Helium COPV on Crew Dragon.
Edit: after checking because of Someones comment, it turned out that cigarettes do not explode when drenched with LOX, they just burn brightly not unlike a flare.
In retrospective, a launch abort tower may hav been better and safer solution, those internal superdracos may make it very hard to get back in the game .....
If it's something like a pressure issue, it could be similar to what happened to AMOS-6, where there was buckled liner in a COPV [1] tank that caused a liquid oxygen buildup [2]
Someone on reddit captured the frames before and after, it looks like it's originating from just near one of the Super Dracos [3].
[1] https://en.wikipedia.org/wiki/Composite_overwrapped_pressure...
[2] https://en.wikipedia.org/wiki/Amos-6
[3] https://imgur.com/G0iE6Rr