Believe it or not, EPSON says that these items should be replaced as a common matter of Normal Maintenance!
I bet you guys never heard of that RIGHT?
Well apparently it is true.
So if you are experiencing ink globs or unexplained loss of any of the two blacks, usually it is the Photo Black, then you need to look at these two possible causes.
There are only two options other than buying a new printer.
Have the Ink Delivery and or Dampers replaced by EPSON and you will need a full or nearly set off carts to be able for them to also refill the new ink delivery system with fresh ink.
EPSON is not about to give you that for free.
Either you provide the inks or they will charge you for a new set on top of the near $800 it will take to do the job.
Your other option is to do it yourself.
With the $200 ink delivery system and the Service Manual on hand and a bit of NERVE, you can try to do the job.
Several have done it successfully so it is not impossible.
Anyway these problems is occurring more and more with the PRO3880 and R3000 and I do HOPE it is fixed in the P800