70,000 miles is very young for a M103 chains(should easily go 2 or 3X that). It's tossing money away. But, they should have done a valve job and replaced the guides as they are soft on early M103's and wear out quickly.
I think it would be wise to investigate. For me, I'd look at buying only a factory tensioer. Maybe they messed up the old one when they re-set it somehow. Don't know how..