Wayne covers this cold startup issue with the OSMO Action 4 recognizing USB-C microphones.  He identifies two popular microphones that the OSMO Action 4 has issues with.  It's best to watch him demonstrate the bug.

What is hte issue.  Are you saying that 3.0vdc in a rode or DJI mic will not instant activate the OA4.

Ah so on start up you do not see the green bar  the relivant team needs to get involved wish them the best of luck!

TLDR: The issue is that certain microphones are not recognized from a cold start; the camera doesn't recognize the microphone.  However, if you power off the camera, power the camera on first, then connect the microphone all is well.  If you *then* power the camera off then back on it does recognize the mic.   However, if you pull the battery, re-insert it, and power the camera on with the microphone connected it won't recognize it again.  The two mics that he identifies that are affected by this bug are the Deity v-mic d4 and the Senheisser xs lav.  There are likely more but he states he just doesn't own every USB-C microphone to test them out.

understood, thank you,  good luck with DJI  correcting.

Fishycomics Posted at 9-27 10:51
understood, thank you,  good luck with DJI  correcting.

I'm just posting this so that DJI sees it.  I don't use those mics.  I honestly hope they fix the other bugs I've reported first, especially the serious one with timecode seemingly dropping frames.

Andreas made a thread about this with same video here: https://forum.dji.com/forum.php?mod=viewthread&tid=298189

It doesn't matter if it's posted twice, as long as it gets fixed.

johansenfoto Posted at 9-27 12:26
Andreas made a thread about this with same video here: https://forum.dji.com/forum.php?mod=viewthread&tid=298189

Sorry, I didn't see that one.  I've been posting as many bug reports as I can.  Hopefully they'll fix it.

ronj Posted at 9-27 18:00
Sorry, I didn't see that one.  I've been posting as many bug reports as I can.  Hopefully they'll fix it.

No problem, just mentioned in case you didn't know.

But DJI only mention that they support 2 adapters, so will not say it is a bug.

what DJI will say, we tested our mic out and works.  

I've just been out and done some testing with the Rode Wireless Go II by a waterfall which was creating a lot of noise and the test footage draws me to the following conclusion:
- Power on the camera, and the recording using the Rode works fine with no cut outs
- changing the gain on the Rode for some reason seems to make no difference to background noise 9Could be because its using USB-C)
- On quick start the audio fails after about 40 seconds and given the background noise of the waterfall at this point I'm convinced it was using the internal mic, not the Rode, even though it was connected.  Also when I changed the gain on the Rode mic during this test, the sound would cut in a for a few seconds, then cut out again.

I believe this is a software issues in the OA4 when using quick start that needs to be addressed by dji

I have the test footage if anyone at dji would like to see it

Unfortunately it looks like the RODE Wireless PRO is one of the USB-C Microphones with this issue: https://forum.dji.com/forum.php?mod=viewthread&tid=299283