Use sp_downgrade to downgrade Adaptive Server 15.7 ESD #2 to an earlier version.
1> sp_displayaudit 2> go
Downgrade from Adaptive Server 15.7 ESD #2 to an Adaptive Server 15.0, 15.0.1, 15.0.2, 15.0.3, or 15.5. Downgrading to versions of Adaptive Server earlier than 15.0 is not supported.