Printer problems

It is a problem very familiar to users of inkjet printers - particularly, it seems, users of high end Epson photographic printers:  blocked nozzles.

My printer has been remarkably reliable for most of the 4 years I have had it, but in the last two or three weeks has developed some very obstinate blockages.  I have tried all the cleaning techniques I am aware of (thanks to the internet), used virtually a whole bottle of "Magic Bullet" head cleaning fluid, large quantities of ink during cleaning cycles and lots of patience over many days, but I have been unable to clear some of the nozzles.  Although I have managed to produce a large quantity of prints with no visible defects, at least one print has the tell-tale lines which I cannot get rid of.

If this persists, I fear I may be looking at the expense of a new printer.