camera modes accidently changes when taking pictures

all my iPhones have had this same issue: the camera mode switches when I put my big thumb on the shutter button. The mode slider and shutter are too close together. I go to take a photo, but the mode has slid to video, or portrait or whatever. There needs to be a way to LOCK the mode so it isn't accidentally moved between pictures. It's also a problem using the macro wheel. my thumb holding the camera moves the mode while my other hand is trying to move the wheel. Arrggggh. A double tap lock?? easy, no real estate involved, keeps camera on the desired mode setting, minimum software engineering involved ...