In the meantime, some more info might help the more knowledgeable members find an answer. Are all the strings detuning or just some of them? Are the strings new, how old are they? Are the strings properly wrapped around the tuning pegs. Can you see/feel anything out of normal in the machine heads?
It might be time to see that tech again...good luck!
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins
-- Chet Atkins