Greybeard

If you press the button at the top on the back of the camera marked marked "Drive Delete" it will show "Advanced Filter". Use the joystick to scroll up to something like "Still Image"

looks like the sensor needs cleaning - as @jerryy said its something you could do - sensor cleaning kits are available - or ask your local camera store to do it

I’ll ask the same question as last time - did the problem show up after you transferred the file to a computer and how did you transfer the file?

Maybe I’m missing your point but if you choose Advanced Filters with the drive button then you can’t choose none - you need to choose some other drive option like Still Image

Advanced Filters are selected (or deselected) using the Drive button

Have you tried repeating the firmware update via the card? I have no idea if it will work but might be worth a try.

Could you share an example? Preferably a link to an original image file - it could be a mark on the sensor. Is it always in the same place?

Its the same as other X series cameras in the Image Quality menu - two types: High ISO NR and Long Exposure NR

what exactly are you doing and what exact steps are you taking? when you say you "import to Lr or my phone" do you mean you are importing to LightRoom on your phone? what sort of phone and how are you importing the image files?

Press the Drive/Delete button on the back of the camera and select something other than BKT https://fujifilm-dsc.com/en/manual/x100vi/about_this_camera/parts/#drive_button

In order to use AF-ON/AF-C for back button focus you need to detach the focus action from the shutter button. In the menu here: https://fujifilm-dsc.com/en/manual/x-s20/menu_setup/button-dial_setting/#shutter_af Once the focus action is detached from the shutter button then AF-ON controls focus.

Are you sure? Does the main battery prevent the loss of settings if there is a defective capacitor and the camera is turned off?

There is an internal capacitor that supplies enough charge to keep the settings when you turn off the camera. It sounds as though this needs repairing. (I'm assuming you keep a fully charged battery in the camera? The capacitor can lose power if the camera is left for long periods without the main battery being charged)

I went through this same problem some years ago with the X-T2 and bought the first version of the Fringer adapter that jerryy has suggested. It has worked very well - and given decent AF performance as well as controlling the aperture.

Are you using custom settings perhaps?

The manual says it works the same as X series. "Each time the shutter is released, the camera takes one shot and processes it to create copies with different film simulation settings, chosen using A SHOOTING SETTING > FILM SIMULATION BKT."

That is the way its designed - if you want to access files on the camera card you will need to transfer them to a computer

I've found the FujiFilm service centre to be quite responsive with questions like this: https://repairs.fujifilm.eu/en/fujifilm-repair-centre/

Yes - I've had to fix apps I've written that worked OK with Sonoma but give obscure and undocumented error messages with Sequoia

Does the camera report the write errors? How do you know its the Delkin card that is the problem? Have you tried using the Delkin card on its own - do you still get errors? I have that exact same card and haven't had problems - but rarely shoot video. The only problem I've had thats remotely similar was with a particular combination of two cards in the two slots - either one was fine on its own - switching to a different card in slot 2 solved it.

Too late - I can live without X Raw Studio for a while - it makes you wonder how much testing Fujifilm carried out while Sequoia was in beta.

I have the same problem but only since upgrading to MacOS Sequoia - Fujifilm has a note on their website recommending not to upgrade to Sequoia with X Raw Studio.

Can you post an example? preferably an original file?

Does it playback in the camera? What happens if you try a test now - take a video clip and immediate try and play it back in the camera?

The only solution would be to change the profile to match the RAF settings - or just let the software make that change for you.