I suspect the photos are of the chain when in the front small ring. To have this much chain wrap going on and the chain on the large ring is odd, WAY too long a chain. So if the shot is when the chain's on the small ring you have another issue not yet mentioned. This being that you're in "cross over". Meaning that the chain is spanning from the outer end of the rear cog set to the inside of the crankset. This amount of chain angle can often cause, when back pedaling, the chain to want to derail. The best solution is not to use this combo and also not to backpedal if in it.

If you are using the cross over combos you will find a very similar combo, ratio wise, where the chain is FAR less crossed. Often a couple or three cogs larger in the rear with the larger ring will be a near perfect match to the cross over's effort (ratio). If you're good with math you can simply count the teeth on each cog and on the rings and run the ratios to see where the overlap combos sit.

Some chain and cogs are more susceptible to this derailing, some less. A cog set's ratchet's ability to freely spin (the freewheel or cassette's body) as well as the der's pulley wheels ability to freely spin also come into play. But the best way to insure minimal back pedaling derailing is to keep the chain angles straighter.

BTW- two more points. Why aren't you down shifting to an easier gear when stopping? Do you like rolling off in a high effort gear? Second- the chain and gear set really needs to be cleaned! It's like changing your undies when going to see your Dr. or brushing your teeth before the dental visit. Andy.