Thank you for the prompt response, some further progress and have been able to isolate the specific scenario. I ensured no other applications were open while ST3 was open ( I use this iPad for gigging now so don't have any comms/notifications enabled that might create momentary ducking or embarrassing noise ;-), unfortunately same result.I tried reinstalling the app and same outcome.
So more detail on the scenario, I am trying to implement a click track so are utilising a multitrack song. For trouble shooting I tried creating a single track song with backing track and disabled combine USB/Headphone option in settings and was able to achieve expected normal volumes with everything at unity gain. (A little dance ensued)
However as soon as I reenabled combine USB and headphone audio the volume issues returned, so does seem specific to this scenario. I even tried boosting the volume to 6db on both track files in the multitrack and no dance this time.....
Any ideas on why that option being enabled is behaving that way. I am using a 2017 iPad?