5.5.4 Cooked and Editor Static Mesh .uassets throwing errors, 5.3.2 was fine - Failed to parse this file! SystemFormatException:...

[Maja-dev]

Describe the bug
I'm having issues opening the 5.5.4 static mesh uassets that I cook for a game mod (MotorTown).

Static Mesh .uassets cooked using custom build of UE 5.3.2 were working fine and opening just like the original game .uassets exported using FModel. The only errors coming up were about the missing materials, no big deal. Uncooked static mesh editor uassets were also working and showing the same details as the cooked ones.

Static Mesh Assets cooked using both a clean and a custom build of 5.5.4 throw errors when opening the mod cooked and editor static mesh assets. Exported cooked static mesh .uassets from the game running on 5.5.4 of the same model are also giving the same error.

5.5.4 Blueprints related to this model are opening just fine, like the ones from 5.3.2. Data Tables and textures seem to be working fine as well.

To Reproduce
Steps to reproduce the behavior:
UAssetGUI Prob.zip

1. Open ZIP that I provided, navigate to 5.3.2 Assets/Cooked/Body_6x4 - Works with both 5.3.2 and 5.5.4 mapping.
2. Try to open 5.5.4 Assets/Cooked/Body_6x4 - Won't open, one error popup
3. Try to open 5.5.4 Assets/Editor/Body_6x4 - Will open after 4 pop ups, badly formatted with unknown values.

Expected behavior
Open the 5.5.4 static mesh assets without any problems, like the assets from 5.3.2

Screenshots
Cooked static mesh from 5.3.2 - Expected behavior. Looks a lot like the 5.3.2 uncooked version from the editor

When opening 5.5.4 cooked static mesh uassets, this pops up and the GUI remains blank

When opening 5.5.4 uncooked static meshes from the editor, one pop up followed up by another. After those 4 popups this appears in the GUI

Desktop:

• OS: Win 11 - 24H2 - 26100.4061
• Version or Commit: 1.0.4 - 8d3cd20

UAssetGUI Prob.zip

[Maja-dev]

Noticed that this is also happening to some .umaps. It fails to open the main map file which is quite big in size, it opens the 5.3.2 version without any issues even though it's a big file.
Instead of including the main map I've included two chunks of the map for each of the UE versions. Only one of the two chunks from 5.5.4 opens where the other gives the same System.FormatException error as shown above.
Both of the same chunks from 5.3.2 are opening.

UAsset Prob umaps.zip