Save to Camera Roll reduces image quality

When images are 'Saved to Camera Roll' from Lightroom Mobile they lose quality.

My workflow is:

1. Transfer images from Sony camera to Sony Play Memories.
2. Save images to camera roll.
3. Import photos to Lightroom Mobile
4. Edit them
5. Select multiple and save to Camera Roll.
6. Upload them to Instagram

When they are uploaded to Instagram, there is a noticeable loss in quality.

It seems there is a big drop off in quality when the photos are transfered from Lightroom to Camera roll. I can tell the difference when I compare the images to the ones which are shared straight to Instagram from Lightroom.

I need to go through Camera Roll because you can't upload multiple images to a post straight from Lightroom. Only one at a time.