Thanks for the feedback. Problem now resolved here by reverting to 5.6.0.3 (and yes have restricted auto updates to "Critical or stable".
However reversion was not straightforward - the old BI version refused to install as Blue Iris was running, and when using Task Manager to stop it, it...
I had the same problem but helpful BI staff explained why... The Perspective BI app now needs Android v8.0 or higher, and I was trying to install it on a lower spec model... So I recommend checking your Android version....