1) The unit could be faulty. Beg borrow or steal another one, and see if it does the same thing.
2) There may be a problem caused by not using the correct power supply. We STRONGLY recommend that you do not use unapproved power supplies. But, to be fair, a power supply problem is more likely to affect the wet signal, not the dry one.
3) Most likely – you may have some kind of cabling issue – try different cables, making sure that they are mono type (tip and sleeve, no ring).
If all else fails, contact email@example.com, especially if the unit is less than one year old.