Hello,
It would be very helpful if you could save the data captured by tcpdump on your DHCP server into a PCAP file (use "tcpdump -w filename.pcap ...") and share it here - it would help us see the contents of your DHCP Option 82 the way they are.
Regardless, however, I suspect that the string in the Remote ID suboption is preceded by two bytes - one is the a type identifier (since depending on the platform, there are different Remote ID formats available - MAC, hostname, user-defined string), and the other is the string length. If this is the case then it won't be possible to prevent the switch from adding those two bytes there. Instead, it will be necessary to configure your DHCP server to simply accept those two extra bytes.
Either way, let's focus on getting that PCAP file and sharing it here if it is okay by you. We'll be wiser afterwards.
Best regards,
Peter