API Problems from the command class

When called get_battery_curent() send_system_temp(), and more or less any other API which returns data I get the rather cryptic message “error in 0” However I discovered that if I call send_system_temp() a few times and just ignore the error then get_battery_curent() and temperature works fine.

error in 0 looks like it might from from receive_command() in the command class. Suggestions most gratefully received. (Yes I have upgraded to the latest version of the API)