I was seriously thinking about buying litchi, but after reading some comments about people loosing their drones when using it, I start to wonder if I should buy it.
I usually fly in mountain region with lots of tall trees, so sometimes I get signal lost and having the RTH working automatically is a must for me. I would use litchi mostly for setting waypoints flights to areas where usually I can't do a normal (FPV) flight due to loss of signal.
What do you guys think? Should I take the risk?
PS: I have a P3 Advanced.
I fly waypoint missions in mountainous terrain a lot and I would suggest you think about the situation and risk a little differently... waypoint missions are designed to follow the waypoint path regardless of signal loss. Sounds like this is what you are looking for and this is a good thing (if it didn't work like this then your mission would be aborted as soon as you lost signal - pointless). You can set it to RTH at the end of the mission if you want to and it will do that fine, regardless of signal loss.
So 'non-auto RTH during waypoint' is how it's supposed to be and is not a reason to worry about losing your drone. I would say the top risks that could lead to loss are...
1) Risk of hitting terrain
2) Risk of weak/lost GPS signal, meaning that neither waypoint mission nor RTH would work
How to manage these risks...?
1) Terrain
My strong recommendation is not to fly 'desktop' missions - i.e. ones that you plan at home based only off google maps. In mountains it is much easier to accidentally program a mission that flies straight into something. It is hard to account for elevation and, though there are ways to do it off google earth, the margin for error in mountains is way smaller than in other areas and it's difficult to be sufficiently accurate. Secondly, in mountains the google maps satellite images are not super-accurate. They are actually taken at an angle rather than straight down - so the image of the top of the mountain is not directly over the true GPS location - this negligible on low gentle slope hills, but a big discrepancy on tall steep slopes.
Instead, I do plenty of reconnaissance flights and create the mission waypoints in the air whilst flying at the real location (easy to do, just set up one of the buttons on the back of the remote to drop a waypoint). That way you ensure that the location and altitude are definitely safe (also a good chance to check out camera angles, check for obstacles etc). You can then go back and edit points of interest, behaviors etc. You can do this over multiple flights. ( And you can do it from different take off points but be very careful there to adjust the waypoint altitude for any difference in takeoff altitude.) I usually use 1 or even 2 batteries to plan and set the flight then put in another fresh one to execute it.
2) GPS signal
The risk is that mountains or cliffs suddenly obscure satellites as you go behind them. Same method as above covers this also - if you've flown successfully FPV in P mode at the location then you will know that the GPS signal is OK there (remember that satellite counts differ slightly over time so keep a margin of error).
A couple of other recommendations... firstly, avoid relying on RTH to get the drone home at the end of the mission - again, mountainous regions carry more risk of the RTH altitude accidentally being insufficient. I make all missions 'circular' - i.e. the final waypoint is back at the takeoff location. That way I know the path that the drone will follow and know it is safe. I still put RTH as the endpoint behavior, but I intend it as a failsafe in case i somehow got my mission plan wrong. Secondly, 'hands off controls during autonomous flight' - especially if out of range. The risk is that you think it is out of range, panic, hit the throttle, switch back to p mode etc and it turns out that it is in fact not out of range and the signal reaches the drone with unintended consequences.
Hope that's of some help... so in answer to your question: I recommend you get litchi, learn in detail how it works, and manage the risks... happy mountain flying!