It is great to see such a fantastic harsh thrashing given to your shemale slave. I like the fact that you give fast strokes with no chance to let her recover between each stroke. This builds the pain to an excruciating level. You should continue this until the slave is screaming and begging for mercy. If she won’t keep still then put her in tight bondage.
If she won't take her punishment like she's told to, she should be tied down and incapacitated. She keeps getting out of form. That causes you more stress, trying to keep the strokes even and works you to death. She should be getting the punishment, not you... And I don't know what it was that she did to get punished for but 5 sessions tells me it was serious. I admire you for your perseverance!