I think we need more information.
Retraction is a key perameter for the blobs. If you have a bowden extruder be prepared to use numbers nearer 5mm. For direct extruders you can still use value as much as 3mm.
210 could be high for PLA. Some are running 185 but this depends on your machine. If the temperature is high you may get more oozing that apears as a blob.
If you set the start point to random the blobs wont align and look like a seam but you will still need to investigate the retraction etc to reduce blob size.
Other factors are mechanical but can be afected by Accel parameters though i am no expert on those.
hard to see from the picture what the filament path is but it looks like it could be a single perimeter so have you got retract on layer change selected.