Coolant smell in cabin - Again?!

[Lacostas]

Hello folks,

My story is somehow weird, since last year my Boxster 986 2.7(2004) started losing coolant and having the smell inside cabin. Went to Dealer and got charged ~$500 for new central heat exchanger (the one under the central dash).

Now the car is losing coolant again, and the smell is slowly/slightly coming back in the cabin from the vents.

How is it possible that it failed again after 1 year?! If it was the water pump leaking coolant, then there should be no smelly cabin, right ?

Thanks in advance!