That’s a logical explanation – I can’t think of any other reason for this anomaly. I would test this with mine but I don’t have a controllable input device other than the OneRemote radio which may behave differently.
Or maybe your DVD1 with the custom cable?
Another thought for tests if you feel like it. The Oneremote can be setup to AAL. Could it communicate directly with the BL3500? And maybe the same with the DVD1.