Hello,
I'm new in this forum and since I've used the 4.5 version I just installed the new 5.3 Professional_5.3.15.28130 version. Unfortunately I have some troubble:
1 - Plants especially trees looks graphically badly - it remaind me FS98 but worst.

2 - Problem using the view around the Virtual cockpit using the key combination Space + mouse movement to move the view all around the cockpit as usually used with the preview 4.5 version.
I linked my video record to show accurately the troubble.
As you can see in the video It seems a problem caused using multi screen view.
I always used dual screen with P3D: the Main monitor to view the cockpit and the secondary monitor to drag 2d windows such FMS, Radio panel, Altitude and so on. So when I open any 2D instrument pop up like the radio panel on the F22 (your default aircraft) and I push the keeboard Space kay and the movement of the mouse the view of the cockpit flip over. When I do the same undoking the 2d panel and draging it on the secondary monitor the cokpit view flip over and ther's no way to recovery.
This is the first time to have this troubble and I dont have any reference with previews v5 version because I moved from the 4.5 to 5.3 version.

Below the link of my video from my Mega account:

https://mega.nz/file/iVkCEJbS#XsGolG7vg648tDCUCYO979MySGKJHQsqsPtl-V5kySc

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I do confirm that the problem I posted is not my only problem but asking some users friend they have the same trouble. Consequently I can say the problem concern a bug of P3D v 5.3. 
I hope the developer can solve this soonest but as I heard usually the prepared 3 D staff doesn’t pay much attention at the users report. Which is not a good things.