Purple blotch, banding

[MarcM17]

Recently I've been running into an issue where after problem-free processing, when scrolling through images, some will have brief purple banding or blotches (I'm not sure what to call it) in the background.  After a second or two to purple disappears and the images appear normal.  The problem persists however when images are synched and the purple appears in the synched photos (on the LR app, and in web linked content).  Below is an example.  Any suggestions would be appreciated.  Thank you.

https://lightroom.adobe.com/shares/150a862895034ff79309ba1ac31e6b92

[GoldingD]

I see the Lr icon, as opposed to the LrC icon. What version of the software do you have?

[MarcM17]

Processed in LrC 13.0.1 and then synched.  By way of comparision, screenshot below of image in LrC.

[dj_paige]

Unfortunately, the answer is not what I hoped (and probably not what you hoped)

https://community.adobe.com/t5/lightroom-classic-discussions/photos-show-banding-when-viewed-in-the-...

[MarcM17]

I should note that this has only become an issue in the last couple of weeks. Older photos using basically the same workflow do not exhibit the banding/blotching.  V13 issue perhaps?

[Jao vdL]

Looks like you found the answer already but yeah this is due to the limitations of smart previews and creating jpeg previews from them instead of the original raw file. Adobe uses fairly low quality for the previews on the lightroom.adobe.com website (actually it might even be avif instead of jpeg). Unfortunately Classic will not upload full raw files. You can use Lightroom CLoudy to upload the full raw (it should automatically connect it to the existing smart previews) and that should help with this issue but won't fully get rid of it. Lightroom web and cloudy is prone to showing banding issues even with full raw on the site. 

Add your voice to this thread to demand full raw capability from Classic: https://community.adobe.com/t5/lightroom-classic-ideas/p-should-be-able-to-sync-full-raw-files-to-th...

Not getting my hopes up as I started that thread many years ago and got many many upvotes but Adobe is not improving cloud syncing from Classic anymore which is why syncing is such a disastrous mess.