Why can't I open a .json from version 3.8 in 3.8.99?

I used a tool I found on the web to convert json faster, however even though it is the same version it doesn't open.

What tool did you use? What does it convert?

The error is:

Caused by: hB: Error reading attachment: weapon_clip, skin: default
Caused by: hB: Clipping end slot not found: 82

Look in the JSON for weapon_clip:

        "weapon_clip": {
          "weapon_clip": {
            "type": "clipping",
            "name": "weapon_clip",
            "end": 82,

"82" is not the name of a slot. Change it to the name of any slot and then it will import, eg:

            "end": "hair_hood_be_front",

is a tool to convert skel to json. Since I have many files this made it faster.

When I have time I'll see if it works

If you tell us what tool you are using we can help.