Unwanted seam appearing in prints on FFCP

[Geoff]

Update:
I found the culprit.. it's the acceleration
Left one is without acceleration and right one with acceleration.

https://drive.google.com/file/d/0B0w...ew?usp=sharing

It's a firmware problem and I can't print without acceleration because my prints will last x5

How can I fix this?

Manually with Simplify3D doesn't work? So you press Edit current process, and click the "Other" tab and have tried changing speed down there too?

if that doesn't work you can also try slic3r (not hard, just have to input the bed dimensions really. Slicer profiles do nothing other than change variables, so technically the gcode is the same for all machines that it pumps out, which is a pretty generic gcode, but the prints seem ok, it has pillar supplrt also like S3D.