Images exported from Lightroom Classic CC being resized?

Hi all,

I've googled my socks off looking for the answer to this but no avail. I normally work on images in Lightroom Classic CC from an external HDD. Some of these are synced via Lightroom CC. Today, I'm working on a laptop, not my usual desktop computer, editing a batch of images that has been synced with Lightroom CC into Lightroom Classic CC.

The issue I'm having is that upon export, the image dimensions are being changes, resized to far smaller images. All the RAW images I am working on are shown in LR as 4608 x 3456 dimension - but when exported to jpg it's resizing to 2560 x 1920. All my settings are to maximum jpg output - 100% quality, no resizing - I'm baffled. I've not had this problem before on my other machine.

Any ideas? Could it be because I'm working on synced files rather than directly from a hard drive?

**Edited to add*** I just went back to my usual desktop machine and got this message:

Another catalog (Lightroom Catalog.lrcat) has started syncing with the Lightroom CC catalog.

Repeated switching between synced desktop catalogs can produce unexpected results. This is not recommended.

I'm wondering if this might have something to do with it.