This is definitely an issue when sharing photos from the gallery to iNat rather than importing the photos into iNat from within the app. It’s usually related to situations where the photo is backed up in the cloud rather than the original file being on your device. Are your photos being backed up in the cloud?
Either way, if you can try again and, if the same issue pops up, can you please send us log files from the app? To send log files, go to the About tab in the app and tap three times on the version number. You will then have the option to email the log files to us. Please make sure to refer to this issue when you email the log file to help@inaturalist.org.