When I tested several frames on the nps (JSBSIM) simulator (fe8bbd3), I noticed several unexpected behaviors.
I am not sure whether these are unknown issues or not. Just in case, I would like to leave the issues in here.

-Vehicle type: LadyLisa
-The following flight mode change leads to increasing altitude.
---> Hover mode -> Hover_Z or Hover_C
---> The vehicle keeps increasing its altitude during Hover_Z or Hover_C mode.

-Vehicle type: bebop2
-The vehicle show divergence of X and Y positions after conducting FLIP mode.

-Vehicle type: bebop2, ardron2
-Many flight modes (e.g., Hover and ATT) are not triggered (maybe, bebop2 does not support the modes).

-Vehicle type: ardron2
-Losing attitude control and then crashing on the ground after FLIP flight mode

-Vehicle type: Quad-Navstik, Quad_Elle0
-Fail to takeoff

-Vehicle type: MentorEnergy
-FAILSAFE never be set even though explicitly triggering FAILSAFE mode.

Vehicle type: Quad_Lisa_2, Quad_LisaMX, Minion_Lia
-When I disconnected AHRS, INS, and GPS, the FAILSAFE can triggered only if its flight mode is NAV. In other words, if the vehicle is in other modes such as Hover_C and Hover_Z, the vehicle never trigger the FAILSAFE. But, the Hover_C is still requiring position data from GPS or INS.

-These issues maybe come from my misunderstanding. Please correct me if I am wrong.
-If these issues are bugs, it would be great if these are fixed :) Thanks!