First flipstick I've been there too. There is a timer on the webpages or something like that so you can't go back. So with a long post it a good idea to at least do a ctrl-a and ctrl-c (select all and copy) before hitting the continue button.
If you figure out how to get your post back, let me know.
AllThisIsThat I agree with flipstick's response. Generally you do have some new experiences when you do qigong. They can be a little frightening. When you develop more trust in qigong you can even start looking forward to, or even looking for these experiences. The former is fine, the latter may be a distraction from you meditation. Since you should be focussed on SFQ practice. Which directs you at times to visualize things as you believe they should be, but in meditations you mostly are in the present.
Sorry, back to you question. Many people experience involuntary movement. For me it is usually a little but surprising rapid shift in the hip area. I always take this as a correction of my posture to improve the flow of qi. As for knees shaking, just this summer I had a few days of serious knee shaking. It turned out that I had gone into a much deeper knee bend and my muscles took a couple of days to adjust.
For me only a little upper back soreness has ever persisted beyond the practice itself. This turned out to be another muscle growing issue, and eventually receeded. Good posture uses some muscles more that they were used to. It was never a more that I would have experienced from a little physical exercise, which would worry me.
The new experiences are can be worrysome, but trust in the universal energy and your master's energy to be creating positive changes in you. I haven't had some of your more vigorous movements, but I still council to develop trust in there goodness and gratitude for the healing.
You are perfection.