Weird residuals after GBS ?

Hello everyone again! I open this topic in the hope of receiving an answer or a similar experience you had.

A year and two months ago, my father was diagnosed with GBS. He had a decrease in muscle strength in his legs and hands, but without numbness and tingling. He did not receive any treatment because it was already too late, and doctors said it was a mild case.

The problem is as follows:
In his right leg there is a permanent feeling of tightness that sometimes gets worse. Once again, he has no numbness and tingling in his legs. Every day we go for a walk outside, and after about 200 meters, the legs slowly start to get tired and start to lose balance, sometimes his legs get tired faster, other times later.
I’m worried that his right ankle isn’t mobile, it’s not moving at full amplitude. At a certain inclination it locks and can no longer be pushed. It’s not like that on the left ankle, why is this happening?

And there is another problem:
When the toes flex, stretched tendons begin to hurt. This is like a kind of tightening of the tendons that sometimes accentuates and makes it difficult to walk. This condition of the tendons is permanent, but sometimes weaker, sometimes more pronounced and especially on the left leg. I keep wondering what it is.

Have anybody experienced this or have an ideea about this?
As I said, my dad has atypical residuals in my oppinion.