BP Group Hierarchy forgetting position on creation


I'm running WP 4.7 on multisite with a modified version of the Boss theme. I upgraded yesterday to get up to date from buddy press 2.4x to 2.7.1 - after much fixing the site is mostly good. However, when now creating a group, you can select the 'parent group' upon creation but as soon as the steps progress through creation the parent group is lost and the group is simply created at the top level (even though that should not be possible due to permissions). So basically, the BP hierarchy is being lost from 1 step to the next during group creation. Where do I check and how do I fix this? The bp-group-hierarchy is version 1.4.3 and I'm running php 7.x

I know there's no official support for that plugin and indeed there's a fork which I tried as it states to support buddy press 2.6 but that came with a set of other new problems. Any help you can offer is appreciated.

PS - I can't give you access to site backend as it's a commercial site with sensitive data. Happy to share my desktop through with a local version running over team view.