It’s still an issue that happens sometimes, but I didn’t find it to be fully reproduceable. The same flight plan can sometimes work or not. DECEL can be circumvented by setting the proper speed on the autopilot, otherwise the plane will decelerate to the approach speed and never reach the proper climb/cruise performance. I guess it’s some legacy error in the default MSFS flight planning system. Doubtful if it will be ever fixed, as the system will probably not see any kind of overhaul until MSFS 2024 now. We’ll just have to live with it.