Merge tool in model builder

[FCC_EnvironmentS_A_]

I have a “sub model” (secondary model) that runs inside the “model” (main model).
In the secondary model and in the “Field Names” parameter if I choose for example 3 fields (Field1, Field2, Field3) the “Merge” in the main model works correctly. If I choose 4 fields in the “Field Names” parameter, the “Merge” in the main model does not work correctly.
Field4 does not have the correct data.
Everything indicates that with 3 or fewer fields it works and with more than 3 fields it doesn't work. The 4th and following fields do not have the correct data.

I think the problem may be in the field mapping of the merge tool.

Any explanation?

Sub model

Model

Thanks

Nelson Costa