You can try fluid and filter change first. There is also a chance the flimsy pressure switch discs are torn. However you will have to drop the valve body to fix those. If you do drop the valve body, might as well put in a Sonnax Zip Kit.
Torn pressure switch discs:
My notes on pressure switch discs:
https://www.e90post.com/forums/showp...6&postcount=12
Regarding the Zip Kit:
https://www.e90post.com/forums/showt...php?p=23304080
6L45 ATF and filter DIY:
https://www.e90post.com/forums/showthread.php?t=573490
Other members' ATF tips:
https://www.e90post.com/forums/showthread.php?t=1257476
https://www.e90post.com/forums/showthread.php?t=1918057