4 channel proxy media won't attach

Have a project that was synced in Resolve, had proxies created in Resolve and now needs to be transferred to Premiere for th editors.

It was shot on a Blackmagic Cinema camera (.braw) and the plugin for Premiere to read those files isn't the greatest. So trying to link the created proxies to the offline .braw footage in Premiere to give to the editors, so they don't have to worry about working with .braw clips.

Any clip that only had 2 channels of audio recorded will attach proxies. Any clip that has 4 or more channels of audio won't attach. TC, and duration of the proxy and raw clip are identical. Only difference is that the audio is set to 48000 Hz - 32-bit Float - Stereo mapped to 4 Mono for the raw clip, and the proxy is 48000 Hz - 16-bit - 4 Mono. 

However the clips that have only 2 audio channels are 48000 Hz - 32-bit Float - Stereo mapped to 2 Mono for the raw, and 48000 Hz - 16-bit - Stereo for the proxy, and they attach no problem.

In the attach window, I get a tick by every clip, as though it's found the correct file, but once it's finished processing all the clips, only the 2 channel audio clips are attached.

Everything is stored on an external drive, and copying the files to the internal drive doesn't solve the issue.

Working on Premiere V 22.3.1 (Build 2) on a mac running macOS Big Sur (V 11.3.1). Have also tried it on a mac running the same version of Premiere and macOS Big Sur (V 11.5.2) and it's the same outcome.