Our team will have a look at this, but no guarantees on finding a workaround. Oxygen Builder is functionally doing things in a way that's majorly outside of the norm in WordPress, so they'd likely be the ones to have to provide a workaround for the functionality that they have disabled.

I did see this plugin that purports to re-enable the theme for Oxygen on some pages, but was not able to get it to work within the context of GiveWP Peer-to-Peer campaigns: