If you are still looking for answer? I'm a John Deere user, but what I see happening in your pictures isn't unusual depending on certain correctable conditions. So, with that in mind, I have a few questions for you. Please bear with me as they are very basic troubleshooting questions.
1. Are you using a mulching kit or just side discharging?
2. What size deck does the 25S have and what size deck did the TZ18 have?
3. What cutting height is your deck set to and have you verified the blade height setting while on flat surface like a garage floor?
4. When verifying the cutting height setting, with the blades oriented parallel to the direction of travel, are the blade tips higher, lower, or the same at the front versus the back?
5. About how tall is the grass when you are cutting?
6. Are you cutting while running at wide open throttle or other manufacturer recommended speed or a lower throttle setting?
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