Long time no speak. been so busy and have come back to this now. So I also learned a lot since then and can share that. The device I was playing with I have now changed so it's now an mt6750 dveice running Android 7.
Actually I used Magisk to root this, I removed verity and have tweaked it fine...however I have 1 last issue.
The issue is that if I do not reset my phone after tweaking and removing magisk then it runs OK. Google play is still even certified. However if I reset my phone, which is often because I use it for work, then when it updates all the Google apps, the google store just fails and I cannot log in. I get the dreaded "Couldn't sign in" and blank screen issue.
I have tried everything to get Google sign in working, including:
1. The standard stuff with apps and clearing cache/memory
2. Deleting the host files
3. Checking and double checking the versions of Google apps, in particular Google play services, Google Play and Google Services Framework.
4. I have removed and re-installed all google apps, taking them from an identical stock device that work.
Still cannot get google to sign in.
So, my question's are:
1. Does removing dm-verity affect google play at all?
2. What in build.prop does google play use to check certification and could this be the issue?
3. Is there anything else I can try to get Google play working?