Why can a DDC command work when reading its value fails?

DDC reads and writes are separate operations. A monitor can accept a command even when its reply is missing, malformed or unavailable through the connection. A failed read alone does not prove that the corresponding write cannot work.

Compare the same monitor and command through a direct connection and through the adapter or dock, where possible. If the command works only through the direct connection, the dock, adapter or monitor input may be involved. Use a supported command and check the visible result on the monitor.

A raw DDC read returns a 16-bit value, from 0 to 65535. For example, decimal 4369 is hexadecimal 0x1111. This contains the byte 0x11 twice. If the expected input code is 0x11, the monitor may have sent a malformed reply. The CLI is showing one numeric value. Keep both bytes when interpreting other commands, because some commands use both.

See DDC connection troubleshooting, reading hardware brightness and the CLI reference for supported queries and parameter meanings.