The nature of all dynamics processors (Gates, Compressors, Limiters) is such that when attack and release settings are too low, they can create a type of distortion called chattering, due to rapid opening and closing of the dynamics processor.
Here is an interesting discussion:
"Compressors are non-liner devices and as such they generate distortion by the very nature of their operation. With light compression, this distortion is hardly audible. But with hard compression, you start hearing distortion. 'Hard compression' means fast changes in gain reduction. Fast attack and release times mean faster changes in gain reduction - making the compressor a (far) less linear device, and thus you get more distortion.
As low-frequencies have longer periods (the waveform develops slower over time in comparison to high frequencies) a compressor can actually act within the cycle of a low frequency provided the attack/release are short enough. This reshapes the waveform quite drastically and in turn generates a very audible distortion."