Animate dotted line being drawn and un-drawn.

[flyermcl]

Hi, I want to animate a dotted line that is being drawn from left to right and then "un-drawn" from left to right. I am using "Trim path" and have animated the "End" property from 0 to 100% which works fine but when I want to "un-draw"/make the "tail" follow from left to right and I animate the "Start" property from 0 to 100% the dotted line "floats"/slides to the left. Why is that? I want it to be stationary.

I have been able to counteract this slide by animate up the "Offset" value to -58% by trial and error but I'm sure this is not the proper way to do it. Any ideas why the line is sliding towards the left?

[Mylenium]

Add a second Trim Path animator.

Mylenium

[flyermcl]

Okay I tried that but couldn't get it to work but I found a workaround since the "End"-property works as I want to but not the Start-property; after I have animated out the dotted line, I suddenly rotate the line 180 degrees. Then I can animate the End down from 100 to 0% again and since the line now is rotated the dots now animated from left to right, as I want.. 

But I am still confused to why the dots "drift" in the first place.
Here's a video showing the drifting.