Giant SyncDrive Pro, 85Nm, powered by Yamaha. Rattles

[Belsyde]

Had a Giant Trance X E 2022 with above engine had it a month then it got stolen - motor silent on downhill. Bought new identical bike. this seems to have a knocking like imagine the battery was slack in the downtube (it's not) when going over ruts etc. only seems to happen when i am not pedalling so wondering if it is the motor? I've checked bolts etc and cant see anything loose. If it is this - is it fixable as today was first time out on the new bike and a bit annoying.