What is this material on my roof?

[Valhalla]

We have had our Viking TT (made by Coachmen/Forrest River) for a little over 2 years now so I have really started paying attention to the roof seams and seals. On all 4 corners is this black putty material (see picture) that is still somewhat soft and pliable but is beginning to develop cracks and splits. My questions are...
1) What is this material?
2) What can I use to seal over it?
3) Should I remove it and start new with something else?

Thanks in advance for any suggestions.

 

[Loquincy]

It is the camper world equivalence of roofing tar like for homes, your gonna want to scrap it up and then reseal it with a product like sikaflex 715 roof sealant or an equal product, If you feel like it needs to be done at all.