Ever since P3D4.4 came out, I have noticed some aircraft compatible with P3DV4.x now have invisible parts. And after loading them, and switching to another aircraft, they cause P3D4.X to crash within three to four minutes to the desktop. I believe some of these aircraft are FSX legacy models, but as I noted they used to work in P3D4.x. One example of such an aircraft is the freeware Demoiselle, found here: http://frenchvfr.free.fr/download.php?lng=en&
Another is my freeware trike, found at Avsim. I consider this a bug since the aircraft worked but were broken in 4.4 and beyond. I tried to reinstall 4.3x but that was no longer viable, I could find the client but not the scenery and content. And I found 4.3x's performance a bit better than 4.5 but I still enjoy 4.5. Two aircraft are not a reason not to go forward with P3D upgrades, I just thought I would mention this issue if there is some internal setting or undocumented .cfg setting I can change, or undocumented shader or xml setting.
P3D4.5 is by the way, such an amazing photoscenery platform and I found improvements when I moved it from my bootup Windows 10 hard drive to a new Samsung T5 2TB SSD. I feel the sim will still challenge Microsoft when they come out with their successor to FSX, and for me the sim is great for training and "muscle memory" I use when taking flight lessons in the Light Sport aircraft I fly.