Endocephalus lineatus has priority and is currently valid.
The name changes already dates back to 1949 (!)
http://chrysomelidae.miza-ucv.org.ve/sites/chrysomelidae.miza-ucv.org.ve/files/1949_Separata_54.pdf
The name Endocephalus lineatus has been used consistently by Bechyné (the main author publishing on this subfamily until his death the 1970ies) and by other authors after him.
A recent paper from 2013 is mentioning bigatus being a synonym of lineatus: https://zookeys.pensoft.net/article/3782/
Wikipedia and various other online sources have also adopted E. lineatus.
The name E. bigatus has been made popular through the famous textbook "Insetos do Brasil" by Costa Lima, 1936 (before it got changed into E. lineatus). This has led to many Brazilian authors using E. bigatus, primarily in an agricultural context, probably being familiar with Costa Lima but being unfamiliar with Bechyné's work. At least several of the more taxonomy-oriented Brazilian museum collections however (such as MZUSP) have adopted E. lineatus though.