Verify Compile with multiple sketches expanded will result in an error

Questions:

• An error occurs when executing [Verify/Compile] or [Write to microcomputer board].
• What are the possible causes?

Answer:

• An error occurs when executing [Verify Compile] or [Burn to Microcomputer Board] with multiple sketches expanded.
• Once, close all expanded sketches, then launch and use only one sketch.