I looked on the website but did not see this model.
It says Coreless/Digital on the box. What is it?

Digital Coreless w/Karbonite gears

Hs-5975 LINK

I got this servo and have used it for 3 weeks but it does not center consistently. Is this a known issue for these?

not that I know of....
Check for anything binding in the steering.......


contact: [email protected]

Actually, I did find something binding...
The steering wheel on my radio. I backed out the tension to make the action lighter but it made the center point of the wheel very vague.
The servo I tested after tightening the spring tension on the wheel worked perfectly.

LOL....

Very true....
The radio is also part of the steering....

Did that fix the issue?

The 5975 is fine. I suspect the 5625 might still have a problem because I noticed it before changing over to the radio I'm using now. I will test it wednesday. I hope it will be fine.