When I’m developing engines, I can see that sometimes there are some
400 Bad Request
errors (mostly proxy problems I guess – because of Recaptcha for sure / Maybe other errors as well but I didn’t face them until now) but this is what SER writes into the log section and it won’t retry that.
22:08:24: [-] 1/1 no form at all – https:// test [dot] com/register
So SER thinks there is no form on that page but if it tries once more with another proxy, It will find that form and will try to register/submit.
If I’m right, this problem may ignore many links when there are problems with proxies.