Like others I had a performance drop, deleted shaders, deleted options.lua and played around with settings on the options page and finally screwed something up enough that DCS would not start, just hourglass spinning. So I closed it with "task manager" and deleted options.lua and restarted it. Went through the options page and set everything "I think" to what I had in 2.5.5 . My frame rates were back to at least what they were in 2.5.5. I wonder if there is a file that gets saved in DCS when it shuts down normally that is the problem? Obviously when you close it down with task manager it can't save what it usually does in a normal shutdown. FWIW