The thing is, while Owain does indeed use Odin's assets, he does not use Odin's asset ID, far from it, instead they use their own AIDs.
Owain, Inigo and Severa use their own Asset ID, because they Mercenary and Myrmidom classes are DLC unique things, like Chrom's Lord class, meaning the class has no assigned model and instead they use the model and animations set on their AIDs.
Did you change the MPIDs? Did you rename the .arc files and change the FIDs? Did you port over the classes with Different class IDs and different MPID labels? Did you change their character IDs? Did you give them a new PID?
While not necessary, all of these things have to be done if you don't want them to conflict and crash Hidden Truths when the player uses it.