After a fortnight of an absolute nightmare with the bus and the jumping, FPS drop and frankly it being unflyable and frustrating (loss of control, pitching up down, left right, overspeeding etc). Never had this issue and I've been flying the bus since 2012...
I've pretty much read every forum post about this and set about my own investigations, my system isn't at fault, its getting on for 5 years old now but still on spec.
I'm happy to report I've fixed it and want to report where I found a problem. Simply, where are you running your bus from?
I personally have my P3D on an external USB SSD drive....as we all know since moving from FSX to P3D the size of the install has increased several fold especially when using lots of addons. This appears to be the issue. As P3D made access to the drive for things and the bus did too the drive hit processing capacity, a micro stutter occurred, FPS dropped and the bus went mental.
I've now installed the bus on an internal drive, separate to the P3D install and that seems have really smoothed things out. In addition I also deactivated trueglass (involves deactivating the gauge) and as I'm not an EFB user I've also deactivated the webserver module to keep that blacked out. But my better mileage really did come from the bus accessing a different drive to P3D. In addition I did also delete and let P3D rebuild my shaders folder.
I wanted to post this as to date the developers haven't asked or mentioned a drive access/bottleneck as possible issue or resolution and thought it might be worthwhile letting anyone else scratching their head that this may just work for you! Drive access could be causing the micro stutters! I'm now flying at 30-40fps (externally) locked, with AI traffic models, ORBX, ASP3D and more add on scenery you can shake a wing at!
The bus is back!
PS for all the other issues that people get when selecting a panel state with regards to auto pilot issues/ not following NAV, needing to input a DIR before following the plan. After loading up, load cold and dark. Wait, put kettle on, then go for desired state (mine normally being "turn around state").