RF 24-105 f/4 L - Dust inside rear element?

[gnartS]

Will canon actually clean dust/"things" inside the rear lens element that is absolutely affective image quality.

Looking inside my lens i can see a white blob (almost like fibre) towards the outside and a further smear of maybe dust towards the centre.

It shows clearly on blue skies as a large instinct dark circle at f/10 on my R6 and a very very obvious blob(s) at f/16 and narrower.

Im certain its not sensor dust:-

- The blob changes size as the lens is zoomed

- The blobs still exist but in a slightly different position when used on my crop R7.  Its gone on my R6 zoomed in past about 40mm (its on the top middle edge).

- My 100-400 is clean taking the same test shots.

Lens is about 5 years old, bought new.  Its been there at least a year.

My RF 16/2.8 has  similar but nowhere near as bad issue.

What are the options here ? The lens is far too expensive to dump but its also only about half usable now unless i zoom in or make sure theres no sky in a shot.  Yes i could edit every image but video its even harder.

R6, 24mm f/22. Right hand, top and centre blobR7, 24mm (so 40ish). Centre visible, right visible. Top cropped off with APS-C

[ebiggs1]

"A clean and check does *not* include taking apart the lens to clean the individual elements."

Correct but it will evaluate the lens and Canon will let the owner know if there is a deeper problem. It is a multi-point maintenance service that makes sure optical performance and mechanical performance is where it should be.  When I was full time I had a C&C done several times by CPS. The lenses or camera always came back looking brand new. I am not a person that ever 'babied' my gear. It either did what I wanted it to or it didn't. No in between as it has to if it's your job. However, I never remember having or had a lens with that much foreign junk inside my lens.

[gnartS]

Rear assembly and yes if they want to replace the rear element fine.

But not binning a 6 year old supposed L series lens (that was opened by Canon to replace a front element 2 years ago) and having to fork out thousands for this.
First time in several decades ive ever seen this on any lens