Guaranteed waystone drops aren't dropping

Hi, in most of my t14/t15 maps, I'm not getting a waystone of the same level from last rare OR a level higher (or any waystone at all) from boss. I understand that t15 bosses will only drop t15s. They don't seem to though.

Please fix, waystone sustain at t15 is extremely bad without the guaranteed drops due to waystone drop chance nerfs.

edit: obligatory it's not the filter

This is fixable by changing servers. It resets forcefully all instances for you. Typically (4/5) times this fixes the drops.