From what I understand, only difference between 1.4 and 1.5 was that UHDcache settings corruption.
That other issue, with splotches on reflective surfaces, that one is present ever since Alpha. So if you have some worse UHDcache experience between in 1.5 compared to 1.4, and it is not related to the UHDcache settings corruption bug, then that is very strange :|