Okay, after some sleep i tried it again. Blabla with Lana & Co -> FP Mission Console -> Chose "SOLO". This time it works. I don´t know what difference it was. Strange. But at last it works now. Maybe the best hint is: If something doesn´t work right, go to bed and start over the next morning. Thank you guys for your hints and replies!

I did. Clicked the console / terminal, chose "Story" but same result. No cutscenes and so on. So i left the FP. Abandoned it from my queslog and resetted the instance. After talking to Lana, etc. again, i went to that console / terminal (next to the FP door), again, and chose "Solo" this time. Still the same result. No cutscenes and so on. I´m just instantly standing on that landing pad and hear that chiss guy blabbing via radio to me. No cutscene. No GSE droid. No dialogue scenes. Just me standing on that landing pad with that lvl 1 Ensign. So, sorry, like i wrote in my OP...it doesn´t work. Not in the way to finish the FP chapter wise so you get it indeed completed. You can start the FP on that mission console in any of that modes and you just have tha FP but not the CHAPTER WISE FP (meaning NO cutscenes (approaching the planet, landing the ship, leaving the ship with dialogue scenes, more cutscenes and dialogue scenes during the FP (after bosses) and also no finish cutscenes after defeating the final boss Valss)). I hope this makes my point clear.

- Clicked on the launch button. - Talked with lana, that chiss guy and that Ensign Raina Temple. - My char says "Let´s bring Theron home" and then, instead the cut scene (Planet approaching and landing plus dialogue scene (saw this on youtube)), i´m back on Odessen in that staging area. - 1. ***?! - As having no clue what to do, i looked on the map and went to that door for that new FP. Door is yellow, can´t enter. - Clicked on the console an tried BOTH story difficulty and solo difficulty flashpoint. Same result -> I can enter the FP BUT there are no cutscenes, no dialogues just radio chatter. I have NO GSE Droid with me (like it should be in a solo flashpoint) and just a LEVEL 1 (!) Raina Temple as comp. Went through the flashpoint. Bosses have 1.5 Mil to over 2 Mil hitpoints. Fight´s took forever to finish them!!! - And after a damn looooong, endless fight against the final boss Valss -> NOTHING!!! - Valss is dead. I get some loot. NO CUTSCENES! Enter that shuttle and then -> STILL on the top right corner there is the Flashpoint saying i must complete the flashpoint. - 2. ***?!!! So, let´s summarize: 1. You can enter that FP via the console in Story, Veteran, Master and Solo difficulty.... ....BUT.... 2. You CANNOT finish it chapter wise as it supposed to be. 3. No matter how often you enter that frikkin´ FP in whatever difficulty, after you finish the Flashpoint...tadaa...still "Complete the flashpoint "A traitor among the Chiss"" on the top right corner of my screen and in my questlog. - 3. ***?!!! After years beeing a subscriber i will cancel my subscription now. No more money from me for such a ********!!!! I´m done!