you had break through August and started prepping again, ok - what did you do besides reading MGMAT and taking CATs? Have you come across any challenges this time around? Have you tried to fill in the gaps since your previous exam? Or you simply put the books in front of yourself and started resuming your prep course from the last year and up to that test day's morning, may be
Usually score change(s) in the exam, about 20-30 points for the intervals mid 400 and high 500s at two successive sittings is an indicator of greater/lesser attention rather than strategic change(s), preparation betterment, or confidence boost.
To attain the latter here what you had to do firsthand:
- review your state of mind and preparation ways since last exam
- recognize weak and strong areas, like ego slack to prevent from moving in the test environment timely, fussy approach to PS and absorbing too much data from the questions instead of reading through the required conditions, etc. verbal-wise focusing on one part of test, SC for example and totally ignoring the CR and RC, or assuming false strategy for RC and assimilating wrong concepts on CR/logical reasoning, etc.
- try to remedy your weaknesses by attending them patiently and consulting several competent sources (it could be BTG experts or certified tutors)
- change the exam prep mood from mechanistic to analytic, people may boast that they knew nothing about OG or haven't studied math since college but hold engineering degrees or have extracurricular activities stimulating their quantitative abilities; it all takes time and for one to drill several hundreds of OG problems won't be enough to compete with another carefully analyzing some 50-60 OG questions one-two weeks before exam. You must learn how and why to analyze.
- all this given your prep must be smart meaning your needs for exam should change with your GMAT abilities' upgrade and moving upward to the next levels. At the level of 20s for verbal you are mainly reading for general comprehension, but the level of 40s requires you to trace the model of passage or its structure, meaning how the passage starts and continues to evolve the author's idea.
Please try to come up with these and several more points of self-analysis first and then seek questions from others likewise why such a strong deviation in scores would occur. Finally your situation stands very close to that addressed in Powerscore's CR Bible under the chapter 9 'Resolve the paradox' - my take is that no one will disprove your practice test scores and encourage you to challenge real GMAT score, but one will try to explain that two scores can comfortably co-exist by being just incidental in your case. The reason of low GMAT score is rooted somewhere else, and you need to address facts of your preparation here.
Success doesn't come overnight!