I'm still seeing this issue in p3d only affects PMDG products. I've reinstalled cc libraries and simconnect. The issue has not went away could this be from a windows update?
With "P3D only", you mean you have MSFS as well and you don't have the issue there, or you only have P3D? P3D has less latency on Simconnect than MSFS and, fact you said it only affects PMDG, seems to indicate you are having a completely different issue that is being discussed here.
The thing that is being discussed here, is the GSX vehicles that arrives on the airplane are supposedly not very smooth, and it usually improves by locking the fps. If with "only affects PMDG", maybe you are referring to the AIRPLANE jittering during PUSHBACK? If yes, that's completely different matters, which is related in some way to PMDG custom ground handling and handling of the parking brakes, is somewhat "fighting" with GSX Pushback, which we tried to fix in several ways, like sending fake pushback commands (because PMDG *DOES* recognize default pushback instead), or fake brakes presses, but these are just hacks, the real solution would be PMDG temporarily disable their internal simulation of whatever is fighting against GSX while GSX is pushing, like they surely do when the default pushback is used.