I wondered about that because the coolant bottle is always low but never empty. Underneath the car is spotless, not a leak anywhere.
One of my sons who rebuilds mining transmissions in Mt.Isa tells me that ethylene glycol is the component of coolant that dissolves the clutch plate linings yet I only use coolant that doesn't have ethylene glycol. I'm still clutching at straws I know but lets just see what a new filter does and take it from there.