My gateway has 1.8.26
I have upgraded from 2.4.0. to 2.5.0.M2.
In 2.4.0 I had a couple of addon files in order get it working:
I left this configuration after during and after the upgrade.
The result was that for each OH restart I needed to go to paper-UI and re-enter the security code.
I removed now the addon files and enabled the 2.5.0.M2 TF binding.
Having now exactly the same behavior. Even worse.
Sometimes when entering the security key, the GW goes online and then immediately offline.
I will step back to addon files from 2.4.0.