It looks like there is a bit of banding on all colors shown but the black and LM look the worst. This could be allignment settings for the banding and also the missing nozzles in the two heads make it worse. Now for the ink dropping out after a big area is printed, then that is the ink starvation. Most say change dampers etc. but if there is any blockage in a line that is used to suck the ink into the heads by way of the capping station, then when the heads run out of ink after printing a large area, they can't get recharged fast enough. You said it helped to pause and then start again.
Did it matter how long you paused?
Was a short pause no good and a longer pause better?
If so then you are getting a bit of suction on the heads while the heads are parked so the line is not totally blocked but would still say to me that there is not a full draw being done.
On ny machine the heads print for a while and then will flash over to the capping station for just a split second and that is where the ink gets recharged, and back it goes printing. When my one line (mine was clear) was plugged, the recharge did not happen and the same look happened as to what you are having. As it printed it was a a bit lighter as it dropped off to nothing.
You said you replaced Dampers so I would think its a blockage.
If you can take lines off of the pump and capping station I would make sure they are all totally clean. Again on my unit there are clear lines that don't hold ink that are just for suction.