Diagnosis
You are defining or maintaining a step loop and have chosen Sel.loop block end.
You must define the position and size of the loop block as arectangular screen area. One corner of the loop block was already fixedand the opposing corner is determined by the cursor position.
In most cases, you define loop blocks as one-line loop blocks, but therectangular area is a special case since it is part of a line.
The system first attempts to create a minimal step loop from two loopblock repetitions. However, there is not enough free space for thisbelow the defined loop block.

Procedure
Place the cursor so that you define a loop block which has space fortwo repetitions and repeat the function.