Macbook Pro Problems

Heya,
So recently i had my macbook pro 13" sent away for repairs, the repair sheet came back as saying it had no signs of liquid damage and that the logic board was replaced and my laptop deemed as faulty. It came back after around 9 days and worked for the night. That morning it wouldnt turn on even though it was fully charged, then when i called compu b, they said it passed their tests but i could send it back again. Later in the day i tried to make it turn on again and it did, ever since then its been shutting itself off, going unresponsive and then turning on at a random time of its choosing. Any idea what the issue could be? Is it just the laptop getting used to the new board (Which i doubt) Or is there another issue? (Which i doubt) Seeing as they said they "Tested it and it passed all hardware tests" before it left. If i should just accept ill be without it for another 9 or so days just say so, thanks for any input!