How do I find out what is wrong with my 3 year old knee replacement?

I had my knee replaced in September of 2021 and I'm not at all happy with the results. Aside from the fact that it is very painful at times (mostly later in the day), its always very swollen and I've dislocated it three times (the peg came out of the slot). I'm told that I don't have an infection and nothing is loose. Due to my metal allergy I have a custom knee replacement made by Smith and Nephew. It is basically thier Legion knee replacement that is made 100% out of Zirconium Oxide and a plastic pad. The first time I dislocated it the surgeon did an open reduction (surgery) and he replaced replaced the pad with a slightly thicker one. The other two times they put it back without cutting me open. I feel like these dislocations are related to my flexibility. My PT measured my flexibility at just over 135 degrees. According to what I've read my knee replacement is capable of flexing 155 degrees, so on paper that shouldn't be the issue. My surgeon wants me to consider undergoing revision surgery using a hinged knee replacement. I've read that hinged knee replacements are more prone to failure. Before I agree to another surgery I'd like to fully understand why my existing knee replacement is still painful and dislocates so easily. Unfortunately, my existing surgeon doesn't seem to know or doesn't want to tell me what problem is. In short I need a second opinion and don't where to turn.