After buying a second pistol, only one of them is displayed for a short time. When shooting with that pistol or after making the following sreenshot it appeared.
As I play a lot with Akimbo pistols, I have also run into this problem, sometimes. Anyway, not a very constructive answer since I don't know how to reproduce it, yet ... I guess it deserves somes intentive tests in juggling with pistols as one of my new job is to fix bugs.
I dont think this will help much, but I get this bug alot. The only thing I can say is that I use the #keys for buying. So after I spawn I hit "b13b13" then scroll twice. It goes away as soon as I fire or change weapons.
I might provide a "bleeding edge" version to try to detect this behaviour, by putting debug message, in place I was thinking. At least, in the mod code, I know where it might happen. For those who want to help and are able to reproduce it quite often (even randomly), let me know