Weird. Cheers, Muska.Yes, that's correct.
Something must have triggered it then. I've tried removing and re-fixing scopes, adding tritium sights and then re-fixing the scope, turning off aim toggle etc. It's the same with all scope and rifle combinations and it's only when crouch-walking forwards. Standing and walking forwards is ok, as is crouch-walking sideways or backwards.
It's bloody annoying!