Okay, someone tell me this is not a fluke...

Well, MGMATs utilize a fixed question bank of approx 1200 questions.
First few tests remain tough in both Q and V becoz the software tries to utilizes maximum questions from the range of 600 and above for obvious reasons.

I wont say this is a general trend (cannot be generalized so easily) but yes I have read in atleast 3 blogs that after 3/4 tests in MGMAT, it starts throwing all the eazy questions or the repeated ones from the previous tests because its pool of questions in the range where you were performing gets exhausted.

E.g. if you were scoring consistently around 650 in first 3 MGMATs, all your 700-800 level questions will be finished from the pool, once they finish the test will throw easier ones from 400-500 or 500-600 pool just to finish the total pool.

So as rightly pointed by whiplash better score your SCORES at GMATPREP, the real indicator.

I would advise try giving a MGMAT untimed, you will see more tougher questions thereby realizing whether you actually reached the pinnacle of MGMAT questions or the questions were repeated.

P.S. views are just mine,may or may not be true,read from other sources and just telling a perspective, i am myself using the MGMAT tests for my prep.