Just thought I'd share my story as a perspective on the Wondfo super-early-positive mystery.
In my experience Wondfos are super sensitive and go positive long before FRERs or any other kind of test, and so I personally think there's a chance they are picking up very early pregnancy or seeing chemical pregnancies that other tests couldn't detect.
Last cycle I got six + Wondfos at 6-7 DPO (sure of the dates) and then 10 days of squinters after that, until my very heavy and painful "period" started. One day into this "period," the Wondfos finally went totally negative and they have stayed negative.
Someone suggested false positives, but I think that's very unlikely with 6 lines, the pigment, showing up under the time limit, and the progression of increasing darkness followed by decreasing darkness... I also got a very faint FRER line when I was getting all the squinters on the Wondfos, so I know something was going on with hCG last cycle. To me my Wondfos at 6 DPO and the following week of squinters are consistent with a very early (almost impossibly early) chemical: failed implant early on 6 DPO, and somehow elevated urine hCG later that day, and then as is common with m/c and chemical PG, hCG levels that took a long time to return to baseline. And I think all of this stuff showed in the Wondfos (and that one FRER) until I started bleeding and then all tests finally went negative.
Just my two cents. That said, I used a different batch from you and it is totally possible that the batch you mentioned is just screwed up. Grr! Also, I know a lot of people hate Wondfos, so you are definitely not alone in that frustration!
Have you tested again? Also, is there any way your SO or a friend could pee on one, and you could pee on one, and compare the results? If there is something wrong with the batch, I think this little experiment could provide a clue. If the other person's test is negative, they maybe your tests are the start of something! FXed!!!
First pic: a dry Wondfo from 6 DPO and wet Wondfo from 7 DPO
Second pic: progression of what I believe was my very early chemical