Split or twinned rainbows are rare and usually short lived. This one lasted for at least four minutes. The shower was quite localised and it was not windy yet twinned bows tend to occur more in stormy conditions.
   
The close-up enhanced image below shows unusual features.   The 'extra' bow of the twin is usually thought to be the lower of the pair.   That would be consistent with its formation from slightly flattened raindrops.   The lower bow here looks regular and has 2-3 supernumerary bows inside it signalling small (and therefore spherical) raindrops.

It is the upper of the twins that looks irregular, it has a lumpy appearance with a varying separation from the lower bow. It is also slightly broader.

Perhaps, as in an earlier OPOD, twinning can take place with the 'extraordinary bow' above the regular one. That helps explain the appearance sometimes of supernumeraries inside the lower twin.   But the formation of the 'e-bow' then becomes more problematic.   If from deformed drops, they need to be prolate at least in part.  If from ice spheres the the red of a pure ice sphere bow would be 3.7� further out than that of the water bow red. Additionally the spheres or ice pellets would need to be of unusually good optical quality.