Going off the original post and what you stated maybe it was a typo. But you said the tank is reading 1ppm of chlorine and they tested it in front of you and it read the same thing. I would make sure they are giving you rodi. Because if I'm not mistaken rodi should read 0 for chlorine.
If the LFS is reading 0, how are you getting 1ppm? What else do you have in your tank? If your test result shows 1ppm but the LFS shows 0 ppm that means 1. one of your test result is wrong ..... could be the lfs or could be you, OR 2. If LFS says 0 and you get 1, you are somehow introducing chlorine to your water. RODI should always read 0 for chlorine. I am not absolutely positive on this, but I think chlorine could cause issues with cycling the tank. Also, when you start doing water changes in the future, if you have chlorine in your water it could be bad for your livestock.
Yeah another thing as well. If your topping off your water. What water are you using? Rodi or are you using tap. If your are using tap water 100% that's where it's coming from. The only other thing I can think of is how are you washing your test kits? Are you letting them dry completely before testing?