I don't have any theories. The Rome mint certainly went through periods of sub-par quality control. Flat strikes do seem especially problematic for certain issues. Off the top of my head, I think of the Cordius Rufus Owl on helmet/Aegis type, T. Carisius's Moneta/'Tools of the trade', Hostilius Saserna Female Gallic head/Artemis of Ephesus. I'm sure there are many more, but it just occurred to me that the examples I just mentioned, and also the Plautius Plancus, fall into the 48-46 BC period.
@Bing , I have always liked the treatment of the Dioscuri facing, holding their horses on this coin! Great equestrian scene. I have a couple Memmius from the same family, but from 87 BCE and with a Saturn bust: RR L and C Memmius L F Galeria 87 BCE AR Denarius Saturn harpa EX S C Venus Biga Cupid Sear 262 Craw 349-1