If you are able to do justice to
OG quant and
GMATClub tests then your knowledge/understanding level is not a problem. What seems to be the cause of silly mistakes is jitters.
Are you able to do all the problems in allotted time?
These are what usually cause silly mistakes:
i> nervousness (an easy question midway into the test?)
ii> dividing attention between the problem and the ticking clock/lapse of concentration
iii>rushing to wrap up the problem
One thing that I can tell you from my experience is that if you are at a certain level, you will usually reach that score if you realize that you are actually at that level. Confused ?
What I mean is that you are probably at 46-48 in Quant, but not aware of it. Unless you miss a few questions at the end, you will not fall below 46, that is because GMAT is good at including your errors when calculating your score.
In one prep test I tanked the first 7 Quant questions and still got a 48, and in the next one I got first 10 correct and still ended up at 48. I was really pissed, but also realized that my true level is around 48. No matter how good or how bad I do initially the test gauges my correct level.
Problem arises when you try to gauge your performance on the basis of difficulty of questions thrown at you.
Also realize that you are far ahead of other test takers at your prep stage in terms of your verbal score. Gaining 4 points in verbal can compensate for losing 4 points in quant (though I am not recommending losing any points in any section).
Hope this helps.