If you hover your mouse over the error code in the State Code Monitor of the SCC advanced pages the dumbed down description of a 12.7.1 error is "a transmit problem as occured".
The key here is in the number and duration of occurances.
Weather between your terminal and the satellite can be an issue. Weather conditions between the satellite and your Gateway location can be an issue.
The Book has this to say in regards to a 12.7.1 error code: