When you swing the Bloodskal Blade with a power attack it is suppose to shoot red magic waves. But my sword was not working.
The issues was a conflict with LOOSE behavior files. I have no idea where I got these as all the combat mods I use I make myself.
So this must have been loaded from some very old mod from (last year?) as all the mods I do use now (that are made by others) seem to only have bsa not loose files.
I deleted the following loose files and this fixed the Bloodskal Blade issue:
Data\meshes\actors\character\behavior\0_master.hkx
Data\meshes\actors\character\behavior\1hm_locomotion
Data\meshes\actors\character\behavior\1hm_behavior.hkx