I have had my O3 air unit in my custom built 5in freestyle quad for a couple months now and have not had any problems. I recently had a hard crash and it ripped the O3 antenna off. Thankfully the UFL connectors seemed to still be in tact and I ordered a new antenna from DJI, the same stock one I was previously using. It worked fine at first and did not have any issues until recently I have been having these intermitent issues where when I arm the quad, the video bitrate stays super low around 7mbps and will not go higher even when im right next to it. It is weird because every couple times I could switch the battery or unplug and replug it in / turn goggles off and on, and then it would work completly fine like normal. But now it seems like it wont go back to full bitrate at all. I get the message on the osd that the air unit is in low power mode, even after I arm the quad.
I have a Speedybee F405 V3 flight controller ESC stack and it uses the 3 in 1 cable to plug into the O3 directly. I thought it might be an issue with this cable so I bought a new one and it didnt help. I checked multiple times to make sure the antenna was fully seated into the connector too.
The VTX(MSP + displayport) is set to UART 1 on my FC which I have never had an issue with.

I am still a newbie to this hobby so any help would be greatly appreciated. I tried looking everywhere and I can't find a solution that works. Its weird that it is this intermitent issue and I do not know what is wrong.

A while back I saw some complaints about SpeedyBee F405v3 and bugs regarding SPI blackbox logging and analog OSD not working at the same time.  Also the UART pins not being assigned correctly or maybe even crossed.  Have you upgraded Betaflight recently?  Maybe you have a problem related to that. Try setting MSP on UART4 in addition to UART1.

If that doesn't help, check the plug on the flight controller to see if all of the pins are still soldered to the board.  One of them might be loose.  You could also try direct soldering the cable to another UART.

The Duck Posted at 2-9 19:07
A while back I saw some complaints about SpeedyBee F405v3 and bugs regarding SPI blackbox logging and analog OSD not working at the same time.  Also the UART pins not being assigned correctly or maybe even crossed.  Have you upgraded Betaflight recently?  Maybe you have a problem related to that. Try setting MSP on UART4 in addition to UART1.

If that doesn't help, check the plug on the flight controller to see if all of the pins are still soldered to the board.  One of them might be loose.  You could also try direct soldering the cable to another UART.

Thanks for the response I appreciate it! I was logging the blackbox data, I tried turning that off and that did not solve anything. Im not sure about the UART pins not being assigned correctly because I was flying without issues for months until this crash and I changed the antenna. I have not updated betaflight in a while so maybe Ill give that a shot.

I did already have MSP enabled on UART4 because that allows you to use the speedybee app to open betaflight wirelessly.

I checked the plugs and ports on the O3 and the FC and both seem to be fine. If I can't get anything else to work then I will probably end up directly soldering to another UART.

It seems that the issue is that the O3 is stuck in low power mode even after I arm the quad so it cant transmit the full video feed. I just don't know why.

Again, Thanks for the response if you have any other ideas I would appreciate it!

Do you have "VTX (MSP + Displayport)" on UART 4, or just the MSP/Configuration switch turned on?  Try setting VTX MSP+Displayport for UART 4.

Some other thoughts:  Do you get a "Motors started / Motors stopped" when you arm and disarm your quad?  Does the fly time start after your arm the quad?  Not the one from the Betaflight OSD, but the one from basic DJI OSD.  If you get those messages and/or the fly timer starts working, it means that the VTX is getting the armed signal and so are your Goggles.

Another idea...  Did you make a backup of your Betaflight configuration (dump all in the CLI) and can you restore it?

If you're sure that you didn't update or change anything in Betaflight, then I would try replacing the flight controller.  If it works after that, you can then rule out the DJI O3 VTX.  The SpeedyBee F405v4 might be drop in compatible with the v3.  But of course you will need to solder your receiver, GPS, etc.  It's a lot cheaper than replacing the VTX.

I've only been flying FPV quads for 3 years, so I guess I'm new to it too.  But I can definitely empathize with you.  Sometimes even the simplest problem can be frustrating to diagnose and fix.  And the hobby is really expensive.

So far I have:
*  The camera on my Air Unit glitch out on humid days.  It turned out to be an adhesive that in the camera that was causing the problem.
*  Bought a horrible Skystars stack with a broken FC and horrible ESC with AM32
*  Bought a couple of eMAX ELRS receivers that have horrible range.  Spent hours swapping antennas.  Gave up and bought cheap $10 receivers from Aliexpress and they work perfectly.
*  I somehow broke a TBS Crossfire Nano RX's telemetry sometime after I had a crash.
*  Installed wtfos on my Goggles V2 and they rebooted on me three times, leading to crashing a big 7" drone.
*  Found a bug in Betaflight 4.4.3 and 4.5-rc that causes the flight controller to freeze and had a quad drop out of the air twice.
*  Had a TBX Nano TX's LED light die.
*  One of the gimbals on my Jumper T-Pro broke (wire broke inside the controller.)
*  Made the mistake of buying an SMO 4K (a decased Insta360 camera.)  A really bad camera.

Welcome to the hobby!