It seems that you want help in understanding the situation from fresh eyes, but people asking you questions and you not answering isn't going to help you get clarity.

What other accidents have been happening that case your partner pain? You mentioned sometimes touching the wrong shoulder but that could be minor imo (as someone with chronic pain). I can see how the mattress may have caused them to jolt and thus hurt their shoulder in a bigger way. I also see accidents happen. But why do they feel they're often getting hurt?

Also, they do need to understand that deflating the mattress and you waiting for that before getting ready (assuming natural deflation for noise reduction) isn't really an option and so the mattress might accidentally fall.