Hello, we have set up a few dozen iphones to be used as devices for an engineer ticketing program, basic restrictions have been configured to just allow that app along with settings restrictions so no one tinkers with items that they should not. devices are iphone 7 and 7 plus on ios 12.4. the issue that we are having is an intermittent one but I have personally witnessed it many times now. a phone that has been un used for some time will not show a wifi connection until you punch in you pass code. I have in testing let devices sit over night or for hours and sometimes they do it and sometimes they do not. it seems random. I do not suspect my wifi as the issue because once awaken they hop on and are totally fine. is there any setting that should be checked that can cause this issue?