There is a post or two here quite a few years ago where someone found a reference in an Epson document to an automatic MK/PK switch that the printer firmware triggered if the user hadn't triggered one manually, either from the LCD, or by printing on a different paper type. That post was in response to someone who claimed to have seen this switch happen in front of their eyes. There are few such reports, as it would require someone not to have done the switch for something like six months, and to happen to be there when the switch occurred, if it is in fact true that it happens. IIRC this was on a 3880, so not sure whether it would also be true for a 3800.
If you only print on PK and want to avoid future problems with the MK/PK switch then you have two choices. (i) You can set a diary reminder to do the MK/PK switch back and forth every month or two. The ink thus consumed might be less than a repair. (ii) You could get a refillable cart from IJM and put either their flush solution it in or perhaps Paul's clear solution, and then print enough using just that channel (possible using QTR) to draw the neutral solution through the lines.
