I just did a black ink switch today after a couple months of using matte. A nozzle check print before revealed a very small block in one channel. The switch triggered a clean...and then another clean at which point it said it failed and would I like to try again. A nozzle check at that point showed a perfect pattern.
This is with ANC disabled AND with the latest firmware installed last week.
You cannot "disable" ANC. This is an assumption being made by many but is incorrect. If you look carefully at the menu choices you will see all this is setting is the ANC function during printing ... all you can do is disable ANC being performed between prints. The printer itself always performs a nozzle check after any cleaning cycle you start, and apparently any time you switch black inks. The only way to eliminate the ANC between cleaning cycles is to use service mode to perform the cleans. personally if I were switching inks and it was causing me problems, I would print a nozzle check before I did so, and if anything is "clogged" would use service mode to clean it. Then you at least have an outside shot at the ANC working well enough after the ink switch to avoid extra cleanings.
What you describe are the symptoms of failed ANC checks ... multiple cleanings, with a failed message followed by a perfect nozzle check pattern. (at least perfect to our eye ... maybe not perfect to the electronics of the machine).
This doesn't necessarily mean the hardware itself is bad. I know mine was defective because Epson had me perform some test, and the ANC board test actually failed. But as Jeff has mentioned the ANC is probably over aggressive, which should be addressable with a firmware update. It may be worth a call to have them walk you through the test to verify the hardware itself hasn't died.