SSIS Package truncation and possible data loss (error code: 0xC020901C)
Okay I found the solution after searching and testing many things.
The issue was in the Metadata (the connection between the Source Query and the Data Conversion), the length of the field was not matching the one from the source query anymore, which is to me, very odd as I thought that the Metadata would be automatically refreshed when you save and compile, or when you close the solution and reopen it.

I don't know why this occurred, but now the package is running again perfectly.