I've been riding these Freedom Ryder LC-1s since 1994 and signed up to this forum just now to answer any questions you may have.

Older models (which it looks like you have) have a damper/stabilizer from Enidine. They are not rebuildable but you can get a new one - the company does still sell them. They should be adjustable by flipping a switch near the front. I don't know which model it is, but you can call them and they'll be able to help you
enidine.com/en-US/Products/ADAMain/ (I think this is the right one)

The newer models have a damper/stabilizer from Streamline Brakes. They're originally intended for ATVs.
streamlinebrakes.com/product-category/atv-utv-products/stabilizers/
The difference between the 7 and the 11 models is the levels of adjustability - the 7 has 7 degrees of adjustment, etc. Full open and Full closed should be the same on both models.

Post a close up picture of the stabilizer on yours and I can maybe help you out more.

The stabilizers exist to keep the bike from 'flopping' too easily when stationary.
At speed, the bike is very stable once you get a hang of it and the stabilizer doesn't really do anything while you ride. But learning these an be a little tricky, so dial in the stabilizer for max dampening until your client gets more comfortable getting on and off and can ride at speed. But know that max dampening will make turning much harder: the more difficult it is to lean side to side, the more difficult it is to turn the bike.

The one other major thing I would do is replace the bolt just behind the front wheel between the rider's legs. Get a high-strength steel bolt and replace it every 5 years depending on how much use it gets. Go for SAE grade 5 or higher or Metric Class 8.8 or higher. Another thing about that bolt is the more you tighten the nut on it, the larger the turning radius.

Oh yeah, Freedom Ryder's customer service is not good. It's a one-employee company and he can be pretty bad at responding.

Let me know if you have any other questions.