I have HA running on 3 new iPads and all 3 seems to freeze and I need to shut them down to get HA back up. When frozen I see the HA logo and a count down timer waiting to reload there is also a button where you can reload before the timer expires. Pressing the button or waiting out the timer fails each time and only a re-boot works.
I noticed one new thing yesterday that could provide additional clues. In the middle of the day all 3 iPad’s started to flash the title bar over and over again. When I say title bar I mean the very top of the screen that has the three dots on the right and the icon to open the side bar on the left. I got the flashing to stop by selecting a different view and then back to the same view, the flashing then stopped. Not sure if there is a connection or not. I have been able at times to get the tablet back with HA running by messing with either Airplane mode or by changing to a different WIFI SSID but that does not always work. If I can’t solve this these iPads are not long for my install.
I’m going to call Apple support on Monday about this as it does pretty much happen every night. It’s likely something to do with WIFI and how Home Assistant deals with brief interruptions in signal (I think)
I have iPads and have not seen this. Seems more to be an issue with your network (wifi, router or both). Too little info to give you more advices. This is not in my mind related to HA. 
I know the general feeling is that this is not an issue with HA but I think I have proven that it is just that. Rather than use the HA app for iPad I reach my HA instance using a browser and it does not seem to freeze that way. The only minor issue is the browser address bar is visible and a little ugly.