@Robert Gonzalez yeah this is a real effect and you're right to separate the physics from the config side — both are actually at play here.
The antenna orientation is almost certainly your biggest culprit at 40-60 km/h. BLE modules have a radiation pattern that's not omnidirectional in 3D, and as the platform pitches, rolls, or just changes heading relative to your ground station, you're regularly swinging through nulls in the pattern. That alone can cost you several dB in the worst orientations, which translates to meaningful range loss. Doppler at those speeds is pretty negligible for BLE — you'd need to be moving a lot faster for it to matter. Multipath changing constantly is real but it's more of a variance issue than a consistent range floor reduction.
On the config side, the thing worth checking is whether your connection interval and supervision timeout are tuned for a mobile scenario. If the link is dropping and re-establishing rather than staying connected through momentary signal dips, you'll perceive that as range loss when it's actually a reconnection latency issue. Tightening the connection parameters so the link is more tolerant of brief fades can help a lot.
Also — what's the mounting orientation on the moving node? If the antenna is pointing straight up or straight down relative to the ground station depending on platform attitude, that's a mechanical fix more than an RF config fix, and worth ruling out first before going deep on firmware tuning.
