I had bad block in un-formatted space, before first partition. Blocks 9600-9603 while first partition /dev/sdX1 starts at 52xxx something. That is the part that is unique to each reader and should not be overwritten if copying partitions from another (working) reader. So there was no point for me to remove the partition table.
My reader is working fine for now, no problems with dictionary of WiFi or anything.