JDE Sales Update not writing to Vertex Register

We are on XE. Our Vertex version is 4.1 (pretty old). We use SALES USE TAX and the configuration works and returns the tax correctly. Print Invoice and Sales Update PDF's show taxes calculated correctly. However, when we run Sales Update R42800, it is expected that the Before and After Tax transactions should be written to Vertex Register (RegPreReturnsTable) but for a reason unknown it has stopped writing. The Quantum_Log file indicates that the RegFileInd flag is set with the value 1 which means that the transaction should be written to the Vertex Register. This register is also written after