The fact that extrusion is consistently intermittent at a certain X-Y area is pretty good indication that the ribbon might have a conductor or conductors going open under certain flex conditions, i.e. a certain X-Y position. A nozzle problem is less likely to be correlated with X-Y, especially with symptoms as extreme as this case.
That solution would not work on my new printer. The head cover is different. I was able to use the clips I printed which do an effective job of keeping the ribbon cable from flexing near the connector.