Topic or Information July 2015 - Zebra customers may find that tags with newer Monza4 chips void and older Monza4 tags do not with the same data stream.
Zebra RFID Printers including RZx00, R110Xi4, ZD500R, ZE500R and ZT4x0R
Impinj Monza4 Tags
Impinj released an updated version of the Monza4 chip with a change to the UMI bit function. This change can cause voids when attempting to print and encode using the Zebra Printers.The UMI (User Memory Indicator) bit is part of the PC (protocol control) bits, which is a portion of the EPC memory bank that tells a reader how much data is contained in the EPC. Because the UMI bit is now fixed, an attempt to rewrite it can cause the printer to void the tag.
Details and resolution on the Monza4 Void Issue Read More>>
Source Joe V