[Cause]
The robot is locked by a program and the locked state has not been released. When a KAREL program executes the HOLD instruction, robot motion is paused. The state cannot be released and the robot cannot be moved until the same program executes UNHOLD or that program ends.
[Countermeasure]
For the program that executed the HOLD instruction, wait until the UNHOLD instruction is executed, or forcefully terminate the program.