Gun L39B can't load a magazine

Hi
I started a new random character today -> Bionic Police Officer
By default the officer gets a L39B Gun and a LW-21 magazine for the 9x19mm +P
My problem is this: Is is possible to load 21 rounds into the magazine. If I try to reload the L39B then I end up with a single round in the Gun. There is no way to load the magazine.

I searched a little bit inside the json. At the moment I don’t have a clue about the mod system, but I think the L39B is a vanilla gun?
Here is the json code

{ "id": "l_mp_9mm", "copy-from": "l_sp_9mm", "type": "GUN", "name": "L39B", "description": "A selective-firing 9mm handgun introduced in 2039, Leadworks LLC's L39B provides accurate single-shot placement as well as controllable short-range firepower with its three-round burst mode. Users praised its accuracy and fearsome appearance.", "price": 95000, "ammo": "9mm", "relative": { "weight": 130, "recoil": 15, "durability": -1 }, "burst": 3, "//": "The M93R can go through up to 110 rounds in six seconds, FWIW.", "flags": [ "MODE_BURST" ] },

As far as I can see the entry for magazine is missing. Is this a messed up file on my pc or a general issue?
Code Sniplets to fix that are very welcome ^^

Works just fine for me. Started a new game as bionic cop.
I can (re)load the magazine, and then load the full magazine into the gun.
I can also just load an empty mag into the gun, and then hit reload, and the gun (mag) gets filled with ammo.
Both take equal amount of time.

Game version?
Which mods are you using? I’m thinking maybe one of the blacklist mods, like “No fictional guns” interferes.

I play with Build 4763
In the meantime I suspect my complete game is a mess. If I start a new world I get a bunch of error messages or 'could not find …'
But I was able to fix my problem by adding the magazine in the json file.
Maybe it will be better if I make a clean install of game and mods.

For my understanding. Do the mods overwrite the vanilla json files at …/data/json/items
I am asking because I have no clue what’s the reason for my messed up file.

Do any of the mods have both “edit-mode” : “override” and a copy of “id”: “l_sp_9mm” which lacks a magazine?

[Info about the JSON files: Some of the guns copy part of their statistics from either a generic item template or another gun, using “copy-from”: . The L39B copies it’s compatible magazine list from the l_sp_9mm.]