Did that include setting the line input resolution to 24 bit 96 kHz (instead of 192 kHz). If not, please make sure to give that a try, too. Measurements have shown worse performance of the ADC at 192 kHz (wether in the audible range or not), but this behaviour could change between firmware versions.
Definitely worth it. Power cycling is completely harmless. You don't loose any settings (in contrast to a factory reset) but sometimes is needed to cure issues that appear after a firmware update.
Last question: Did you happen to apply any form of EQ to the line input?