Local Sync Status, Original vs Smart Preview

I am having this same issue but to make matters worse now all the files that are Local Smart Preview won't export. The Original files are all in the same location on my Desktop so I don't know how to fix this and change the Smart Preview to Original. It is also very random, like you said, these are in the same batch, same album etc. 

Much of this is affected by various settings. To start with, what device are you using? I assume you are referring to the Lightroom Mobile app (LrM) on either a phone or tablet, yes?

Assuming that's the case, is the option to "Only download smart previews" (App Settings>Cloud Storage & Sync tab) checked? If it is, then any originals initially stored on the device will be replaced by Smart Previews, and if you use the "Store Locally" option for a specific album, that too will only download Smart Previews. That's a perfectly normal way to operate, I have ALL my albums stored locally as Smart Previews.

Note that should you try to edit an image on the iDevice which only has a local Smart Preview, LrM will automatically try to download the original from the cloud, and that original at some future point is likely to be silently replaced by a Smart Preview. It's thus entirely possible that at any given point in time the local contents of an album on the iDevice could contain a mix of Smart Previews and Originals.

When you try to Export from LrM what happens depends on:

a) The type of locally stored file (Smart Preview or Original)

b) The Dimension setting in the Export Settings dialog

c) Whether the iDevice is online or offline.

Looking at b) above, if the Dimension setting is greater than 2560px (which is the maximum size of a Smart Preview) AND only a Smart Preview exists locally, then LrM needs to download the original from the cloud in order to export at the chosen Dimension setting. But if the iDevice is currently offline then the original cannot be download and so the export will fail. I think that's also the case if the iDevice is not using WiFi but does have a Cellular connection, but the "Use cellular for sync" is unchecked (on that same Cloud Storage & Sync tab in the App Settings).

Note that you can, at any time, manually replace the local Smart Preview with the Original (select the image, tap on the cloud icon top right, then tap on "Download Original"). Obviously the device has to be online in order to do that.

Thanks Jim. Yes, I do have 'Store a copy of all smart previews locally on <my local disk>' checked. This gives me a better understanding of how it functions, though like lots of Lightroom operations it's not crystal clear. 🙂