Without a doubt. If one can't understand an argument they should not make any judgements about its soundness.
There is a way to make at least a guess about the soundness:
Try to find as many other "experts" opinions both in agreement and in disagreement. Looking at the reasons they give, even if your understanding is shakey, and how they come at the problem allows some guess as to the soundness.
Even the vast majority of experts are not always guarenteed to be right (H. pylori being a good example) but if you are having to lay bets they are right more often than not.
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