My Pioneer upstairs mini split won't cool unless downstairs unit is also on. Fan does run on upper unit if downstairs is off. Both units are set to "air" (snowflake) mode.

If ONLY upstairs is on for ~20 min, when I go to turn on downstairs, downstairs unit blows FRIGID air and quickly starts to make cracking noises where it sounds like it might be freezing up (?)

This is new install by a LICENSED contractor. Now they have said they can't fix it and I'm attempting to get another contractor but the nearest authorized Pioneer tech is at least 40 miles away. I have calls into a couple of them. In the meantime, I'm hoping to get ideas on potential problems/solutions while I wait.

Does this sound like wires are crossed at controller?

Any other ideas? I've checked for kinks in refrigerant lines and don't see any. No apparent kinks in drain lines. I know there is no quick fix and doubt it'll get the attention of a professional during the busy summer season...