Slanted round transition

Hi everyone,
As my title above says, this is about rounds that become slanted at the transition.
I’ve been crocheting for a long time now, but I just don’t get it.
Right now, I’m crocheting a sweater in rounds. I close the round with a slip stitch into the 3rd chain stitch. Then I start the new round with 3 chain stitches and continue with double crochets until the end.
I really don’t know what I’m doing wrong. I keep ending up with a transition that always shifts to the right.
Is there a trick to prevent this from happening? Where could the mistake be? Alternatively, can I crochet in rows and turn the work each time?
Warm regards, Marion 

Hi Marion,
welcome to our forum.
If this pattern is from here, you can contact the author or provider via private message and ask for help, or you can send me the link to the pattern, and I can ask for help on your behalf.
  If the pattern isn’t from here, it would be better to ask the author or provider directly for help—wherever you bought or downloaded the pattern—because only the author knows the pattern really well.

If you’re crocheting without a pattern, the readers of this thread might be able to help you.
In any case, I wish you the best of luck. 
 

Hi Marion,
you can avoid this slanted line by turning your work after finishing a round by slipping a slip stitch into the third chain stitch. Then start again with the 3 turning chain stitches. However, you may need to adjust the pattern slightly if you’re crocheting a lace pattern rather than just double crochet. This is because turning the work means you’ll be crocheting in the opposite direction every other round, just as you would when crocheting in rows. 

The previous post should read

“if you’re crocheting a pattern”