I have recently purchased an iPhone coming from Android and placed all my documents on iCloud. When using the File app, I tap on some JPEG files in my Documents folder. They will fase about 5 times, each time if flashes it shows the image briefly, however, after that no image is shown. Sometimes they do not even flash, Files app will only show the loader and the word LOADING right below it, and no preview is shown. iOS version is 15.4.1.
One thing that differentiates one file with a problem and file without problems is the file size. My JPEG with issues on my physical device are way larger at the order of 20 to 60 MB.
If I pretend to share the file and save to iPhone instead, I can view it normally from Photos app, but these are document images I do not want to have in Photos because they belong to a folder with other document types as well, for the sake of organization.
Interestingly, on my MacBook Pro, I open an iOS simulator, in this case, a 15.4 iPod Touch and follow exactly the same steps, and all JPEG files are shown in Files app preview without any issues.
This is an annoying bug as I had personal issues for not being able to open my image document when I needed and because such a pricey product like an iPhone should not produce such a bug for such a basic thing like showing a JPEG file.
These files are not corrupt in any way as I can open them normally if using Photos or on my MacBook Pro, or everywhere else including the simulator in previous iOS release, the Photos app or an Android device.