Problems with dual extrusion using a wipe tower

neoh

So i have dual extrusion set up and working mostly, its set up as a 2 in 1 out extrusion using 1 hotend. I have the extruders, both of them, set up to extract 100 mm. when it changes color moving to the wipe tower, one extruder, the 2nd one, tries to re-extrude more then the 100 mm and the first extruder is not re-extruding enough material leaving a gap in the wipe tower and bleeding the 2nd extruder material back into the first few seconds of the print.. 

Anyone know why on earth my extruders could be retraction the correct 100 mm but not re-extruding the correct amount back when hitting the wipe tower?

Thanks in advance..

Repetier

Don't think it depends on wipe tower directly. Retraction is normally not a problem and can be fast. Re-extruding will hit at the end on plastic or at junction hit something that causes lost steps or filament slip. Just an idea why. Maybe both have the problem but one has stronger motor or more grip on filament. You could try reducing speed for that part. Otherwise steps per mm wrong but then retracting would not be exact.