Art-J's post in P51D Cockpit Display was marked as the answer
Reinstalling is rather a last resort solution, usually not necessary. Runnig a repair command (linked to in start menu shorcuts for DCS) helps in most cases.
Neither of above works, however, if source of the problem lies somewhere in your personal settings folder, because this one's not affected (ergo "fixed") by reinstall or repair. I suspect that's what happens here. The location is C:\Users\[your user name]\Saved Games\DCS (or DCS.OpenBeta - you should have both I presume if you installed stable and Open Beta DCS side by side?). If the view in your stable version is OK and it's messed up in OB, then I'd compare their respective \Config\View sub-folders and make sure the latter is the same as the former.
If that still doesn't help, you can temporarily rename/remove other sub-folders and see what happens (...or just copy all content from Saved Games\DCS to \DCS.Openbeta if you don't care about separate logbooks, campaign progress or whatnot). Experiment at your will, just make backups first.
Art-J's post in TF-51D Trim Tabs Movement Direction was marked as the answer
No, as Frederf noted, they are animated and work correctly, at least in simulation flight mode. Do you use game flight mode maybe? Although I think trims don't work in that one at all...
Anyway, in both Mustang modules (and other warbirds for that matter) they work as expected. Keep in mind the rotaries in the cockpit indicate not the tabs movement directly, but the airplane response to their movement:
a) rudder rotary right -> rudder tab goes left -> rudder goes right -> plane yaws right (and vice versa);
b) elevator rotary forward -> elevator tab goes up -> elevator goes down -> airplane pitches down (and vice versa);
c) aileron rotary right -> left aileron tab goes up -> left aileron goes down -> plane roll right (and vice versa).
Just tested in latest Open Beta version of the game.
Art-J's post in Cold start issue with ground crew in Nellis (and other airbases on Nevada map?) was marked as the answer
I'd start with checking the usual things in the mission editor:
a) is the airbase set to the same coalition colour as your aircraft?
b) are the aircraft radio frequencies set correctly for the chosen airbase (if they need to be set that is - I don't own either of these planes so dont know how radio works in them)?
Art-J's post in External view was marked as the answer
Edit the mission, go to the plane properties and select any loadout other than default "mission loadout" created by Fast Mission generator. These two thingies will disappear then.
@NL or BN - this is what we can see as default loadout for P-51D-30 after Fast Mission is generated. Tested in latest 2.7.1 build. I don't even recognize which module these chunks came from 😄: