In my experience, these are two separate things: "Qigong Deviations" and "Qigong Sickness". Qigong has a way of getting to the root of any disease or imbalance, even if it is latent or unexpressed. Practitioners can sometimes experience sickness or "side effects" of training Qigong, especially beginners, as mobilized Qi starts to act upon those 'sickly' parts of your system. This is, in effect, a healing response and diminishes with further (correct) practice. That's what you might call "Qigong Sickness".
"Qigong Deviations", on the other hand, can occur from incorrect practice (especially of 'Inner Cultivation') and hence deviated flow of Qi, causing physiological and psychological symptoms. There are / were, I'm told, special places in China dealing with these cases. Especially following the Qigong boom post 1949. This is a lot down to the style / school of Qigong you practice - some are more 'safe', i.e. less incidents of Qi deviations than others. Plus, deviation can also be induced if the student attempts to short-cut the system, rushes cultivation, chases 'extra-ordinary powers' and guides Qi inappropriately.
Wild Goose Qigong is one of the safest in this respect. It emphasizes a natural breath and movement (not the mind) to cultivate and guide Qi. But then I am biased