I built an example with water , which imported from unity3d’s package “water pro”. When running on my ipad air, the waves got slowly and slowly as the time past by, but frame rate was fine, about 60fps.
It was weird, so I tried this on macbook, directly running the example at unity editor, and it was all right, the waves were smooth all the time.
It is probably because of the _Timer value increases to float max value limits. Although im not sure if this is the case,
Instead using a custom timer that loops between 0-some small value and passing this value as time solves such issues for me.