In my experience, that is a classic firmware (FW) issue with the P4. Often a failed FW update attempt or a corrupt FW can cause camera/gimbal issues.
Go here to download DJI Assistant 2 for either your PC or Mac:
DJI Phantom 4 – Specs, FAQ, Tutorials and Downloads
1) Install software on your computer and then restart computer*.
2) Turn on your P4 - motors off - and connect your P4 to computer - with remote turned off - via the included USB cable that came with your P4. The port on the P4 is next to where the SD card goes.
3) Open DJI Assistant 2. It should then 'see' the copter. Click on P4 icon. You will then have to login to DJI with your credentials. You will then see a pane that will show you what FW version you have, and it will give you the option to refresh the FW. Do a refresh and see what happens.
It is possible that the faulty SD card you mentioned corrupted your P4's FW, so do this refresh and any future operations with a known good SD card.
*A restart may not be required, so you can try to connect to the software without doing so, but on my Windows 7 PC, I had to restart - probably to load the P4 drivers into the registry..
You never did say if the P4 boots normally with the camara/gimbal going through its normal sequence and then snapping to center. If it does not, then you could have deeper issues, but I suggest trying the steps above next.