I had the same problem as you. I used wiley and averaged 68% on the MCQ's and did almost all of the available ones. Every quiz I took I either got an 80% or a 30%. It was extremely frustrating. I took the exam last week and find out on the 8th if I passed. If I did, I'm done with all of the tests.
Yes, it's been happening to me for the last couple of weeks. Started two days before my BEC Exam, I called and they reset my account. It fixed it temporarily, but has been happening again this week.