We have been experiencing the FlameOuts again even our fuel system was fixed as per the advices given here and we became more familiar with the turbine specifics. The turbine always shuts down at the begining of a flying session/day as soon as we execute one or two rolls or loops, however it runs perfectly right after the same day. Therefore we started to proceed with a "controlled" FlameOut on the ground by holding and moving the model nose up and down with the running engine. Once the FlameOut happens we know can fly safely on a given day. We checked that there are no bubbles going down the visible parts of the fuel system, i.e. thru the fuel tubes leading to the engine so we assume some bubbles might nest somewhere inside the engine and that they can only be released by moving the engine as described.
We would appreciate if somebody has an idea on how to fix the problem. I enlose two recent videos to illustrate the problem - one with the FlameOut occurred during the flight and the other with the "controlled" FlameOut on the ground after which we enjoyed our flying on the day with no more repeated FlameOuts.
https://www.youtube.com/watch?v=XKTw8JEmnkk
https://www.youtube.com/watch?v=cQiKoN7rV90