The app was created in the pre-era of runtime permissions (API<23).
So, I assume that your issues are caused by these (runtime) permissions.
I once took a look at the manifest (project from Jose Luis Núñez):
Something is going wrong there ...
see here: https://developer.android.com/guide/topics/connectivity/bluetooth-le
so, you may have to adjust the Manifest ...
may be you have also to ask for permissions in your blocks (when something (events/functions) from the BLE extension is called). I have no experience with it.
Actually, the current BLE extension should add these permissions (except the red one) to the manifest. Whether these are then also requested at runtime, you must try.
PS: Suggestion: post the aia or upload it to Google Drive and post the link
but the 'old?' when BluetoothLE1 ByteValueChanged came back after not being there earlier today.
And use "Attach a file". This will allow a .aia containing extensions to be uploaded, whereas it cannot be done when writing a new post/new reply.