Your barcode from ZM600 looks good and identical to barcode printed on ZT420. The only difference I able to see is a size of barcode. Seems both could be scanned without any problem. Could this issue to be related to your non-handheld scanner? Say, improper distance for bigger barcode?
Although, there is no ability to control barcode width precisely for most of barcodes, there are some barcode ZPL commands let you select barcode size. What exact barcode type and ZPL command you are using?
Also, could you please to share photo of printed labels? The one that is ok and another that has an issue. I mean real photo of labels, not just barcodes.
Software Engineer, Kutir Mobility
Posted on behalf of Zebra Technologies