In reply to Martin W:
The grab adhesives usually used for that kind of thing are often pretty crap if moisture/oils are present, I expect that your splash back has been there yonks and so the adhesive is pretty well cured though.
I wouldn't bother but you could try some WD40 down the back it might work over time,
one of our technicians disassembled a thread locked vacuum chamber this week, which is probably a similar problem, he used something i've never heard off, he has gone home now. I can ask him on monday.