Rather than taking a picture for image type questions, users can select the folder icon to upload a pre-existing image. However on Android devices the folder location does not show their photo gallery where the devices pictures are stored (this is not an issue on iOS devices). The screen shot below is what I see. Where is the location for the mobile devices photo gallery?
The behavior that you mentioned has been targeted for improvement with the next release of Survey123 for ArcGIS. If you would like to test it out prior to the official release, I would recommend joining the Early Adopter Community for Survey123 and testing out the upgraded Android Photo Gallery functionality. In addition, you can take a look at the past GeoNet forum thread where others were encountering this issue.