Mastic "sinking" - should I be concerned?

[mfork00]

I have a few spots around my pool where the mastic - which just looks like caulk to me? - is sinking. Is this something to be concerned with? and how much urgency to get it fixed (if any)?

Pool is 2.5 years old, 3rd summer using. Concrete patio on left of picture with a spraycoat. Coping on the right is Leuder stone.

 

[AQUA~HOLICS]

The mastic has a very important role in keeping water from getting to the soil below the coping and deck that may cause heaving of the flat work from the soil expanding.
Time wise, completion should be done before any rain storms occur.