Thank you for Saint Jack for the common sense injection
I think many of us experience this problem on aging automobile. (The AS350 is known for using some automobile standard parts, such as the warning horn from a Renault)
I always assumed that with an old belts the problem was that the gue and dirt inside the nylon belt is stiffening up, plus the UV exposure could be hardening the belt.
As the result, when cold, the strap is overwhelming the return spring particularly toward the end when the spring is not highly loaded.
I have this supposition to be discussed:
1/ clean the belt in hot water with detergent and condition it with some silicon lotion (improve softness and friction)
2/ send the whole unit to a automobile seat belt overhauler for a new belt install.
Second choice is probably highly illegal. forget I ever mentioned it
but it's readily available and would only cost a $100 max,
a number of them let you choose your own belt color,
I think car restaurators do it as legal practice
How about the 1st idea, is it possible to do in the context of normal maintenance?