Certain items within assembly unable to change hidden status

Have something weird going on, only applies to a certain assembly.

Its linked to the group i think.

Any of the sub assembly items within that group, i cant change its view status (Ctrl +h / Hide button)

I can hide the group as a whole, just not the individual items inside that group.

 When i try to do that the "hide/view" icon changes (the strike through on the eye appears/disappears) but the actual items are still visible.

i can also hide parts inside those sub assemblies individually.

I can also use other groups inside this assembly as normal, only on the one group.

I cant see anything different within layer tree either.

Creo Parametric 10-0-1-0