If there’s liquid in the spring perch I guess that a damper seal leaking is the most likely cause? If you jack-up the front end maybe you can reach in to the top of the damper to check?
You could always try the “lean and release test” on the wing to gauge the damper’s effectiveness, but the suspension is so stiff that I doubt that you’ll get anywhere with that, so a damper replacement probably is your best course of action.
Hopefully the new wheels and tyres will go some way to address your ride issue.
Jeff

You could always try the “lean and release test” on the wing to gauge the damper’s effectiveness, but the suspension is so stiff that I doubt that you’ll get anywhere with that, so a damper replacement probably is your best course of action.
Hopefully the new wheels and tyres will go some way to address your ride issue.

Jeff