Poor quality of uploaded photos

I have a Huawei P10 Lite and used a USB to connect it to my Macbook Air. I clicked the 'Camera (PTP)' option which lets you transfer photos onto your computer. However, only some of the photos were in high quality in iPhoto and most of them were blurry and smaller than usual. They certainly weren't this resolution on my phone. I have no idea what has happened and why it has only happened to some photos.