'Chain Suck' is caused when the chain fails to dis-engage from the chainrings while pedaling forward. Is there a chance your front rings have so much dirt on them the chain fails to properly dis-engage? Distorted chainring teeth cause chan suck as well, a distorted tooth catches on the chain thus preventing proper release.

I doubt it's chain suck in the true sense of what chain suck is, its exceptional rare to see it on both chain rings.

I think its a stiff link. Stiff links dont always hang up with every revolution of the chain, they can be very intermittant depending on different variable like pedal pressure.