Hello guys.
I found this thread as i was looking for a solution for the same problem.
It is a bit strange since when i first hooked up my supervolcano and Bondrtech DDS estruder i did not experience this problem. Z seam is quite noticeable, but it was to be expected with 1,4mm nozzle and 1mm layerheight.
But then it changed at some point. I honestly dont know what happened, and this problem appeared also for me.
I spent a whole day tuning my settings for PETG with carbon filament to get the seam somehow bearable, and managed to get it pretty good with coast and wipe settings.
But then i started a big print with PLA and it is awful.
It seems like it underextrudes heavily at the start of the layer and leaves a hole to the print up to 5mm long.
i just tuned retraction down, zeroed coasting and wipe settings and try once more.
Otherwise i am pretty happy for my settings since my hollow print with 3mm shell breaks evenly cross seam and along the seam, so i am a bit reluctant to change my temperature settings.
If anybody solves this problem i would be grateful to hear what causes this.
I have been using cura 4.6.1 and just upgraded to 4.8 to see if there is some problem with the software.