Why is job success jumping, despite the fact that I have not had new projects for a long time?

Question

Freelance

On the upwork for several years. Since last September, I have only one project, small, hourly. There may be an hour a week, or less, more often - several hours.
My job success jumps. Then it is 100% for several weeks, then 75%, then again 100%, then 78%. Why? How can this even be? And who said there that if you don’t take on new projects, and work on the current one, then job success remains in place?

Answer 1

zhs is calculated as time, the formula is described in the help, respectively, time goes by, let's say projects are taken for the last three months, time goes old projects fall out of this interval.
if there are no projects for a long time, then zhs will fall to zero, respectively.

Answer 2

a lot of things have been done on machine learning there (as well as everywhere in similar services) - therefore, machine learning algorithms that consider jss are probably changing, perhaps they have implemented another algorithm that is more efficient globally (more orders, customer satisfaction, etc.) but taking into account other parameters, not the same as the previous one.
Well, i.e. rudely: if earlier one algorithm gave high jss for one parameters, then the new one taking into account others - underestimated because The freelancer did not have these parameters.
In the same place, they seem to have no guarantees anywhere that if nothing changes, then jss should remain constant - so they can experiment with it.