Pixillion corrupting files on conversion

[DPWALES]

Using Pixillion 7.4 on Mac. Upgraded from version 6 because of an issue and  find 7.4 has same issue:

1. Images taken from camera card and stored in desktop folder, images are between 7 and 10MB ( nothing unusual)-STANDARD PRACTICE OVER PAST 7 years.

2 Images dropped in to Pixillion and compressed to around 500-999kb-STANDARD PRACTICE OVER PAST 7 years.

3. Images now fail to upload to a Facebook Page-issue

4. HOWEVER if I try to upload the pre compressed files, i.e. the 10MB ones, NO PROBLEMS they load to FB  just fine.

5. Theory says Pixillion is doing something it should not. Tested it out with previously taken photos from a stored folder ( event at Christmas 2019) and  from which I had previously reduced and stored in a "reduced images" folder,  ran the originals through Pixillion again and they are corrupted!

So what is going on? Image info shows no changes other than the size of the image.

Thoughts and or a solution urgently needed.

DPWALES.