Instructions are of variable length, from one to fifteen bytes long.
This means the address you provided may not actually be the start of an instruction. This also means, therefore, that the first few instructions you see may not actually be what the machine saw.
If you look at the output of several unassemblies starting at sequential addresses, you will see that after typically 3 to 5 tries, the unassembly will agree with previous ones, for some point after the unassembly started.
This is typically within four or five lines, but not always. Be cautious, and see if the sequence looks reasonable. If it does, you have most likely found an instruction boundary. Experience will help this process.
Some common sense will help as well. Obviously, an application in ring 3 cannot perform I/O directly. Likewise, the 'db' means that the unassembler did not have a way to interpret this as an instruction.
The last command entered looks at a few of the instructions which actually preceeded a failure.
Can you discover which instruction put the data into the ES and BX registers?