E220-900T22D Config request issue

I am using a E220-900T22D with an Arduino Nano Every. I use that particular Nano because it has an extra hardware serial port (Serial1) so I don't have to use the software serial. Communication seems to work well including configuring the module with M0 = 1 & M1 = 1. However, when after configuring I send the configuration request C1 00 08 to get the content of all 8 registers (00H ... 07H) back for verification I always receive an extra byte containing NULL (0x00). Is this a normal behavior? I couldn't find anything about this additional NULL character in the E220-900T22D manual.