The problem

• When enter into Scale Mode (S) the default values are (1, 1, 1) without any mouse movement enter into Rotate Mode (R) the object Rotates (although not changes any in grebe values).
• So on in Move / Rotate Mode (S / R) default values are (0,0,0) without any mouse movement enter into Scale Mode (S) the object scales becomes 0 (although not any value change)..

Solution

Fix that's problem.
Demo