The distinction is often made between 'due to' and 'because of'. 'Due to' modified a noun, while 'because of' modified a verb. As an example, you could say 'I can't dance because of an injured ankle.', or 'My inability to dance is due to an injured ankle'. It is wrong to say 'I can't dance due to an injured ankle'.
in a simple way, you can take "due to" as "caused by".
The reason why "due to" always cannot be accepted in GMAT is that if "due to" is placed at the beginning of a sentence/subsentence it is lead an adverbial phrase, and that many people consider "due to" is an attributive phrase so they insist the phrase couldn't introduce an adverbial phrase.
我看到og12的解释上面对于该题目是这么写的，“用due to 来引导原因，在这里有点模棱两可，让人觉得是游客的呼吸里的潮湿导致需要repair。 其实文章后半句话阐述了两个使得chambers需要clean and repair的原因：盐分结晶以及真菌生长在墙面。”
因此，我推测下第一点：
due to 这个词做由于解释时，通常紧跟着直接原因，这也就是为什么上文容易产生歧义。
但是用because+that从句，由于从句的复杂性，所以可能可以避免该问题，所以更加合理。（该想法只是我个人的推测，请大家指点）
PS:从牛津高阶英汉双解词典中查到"some speakers are careful to use due to only after verb be, but it is also generally considered acceptable today as a synonym for owing to."
另通过我对于because, owing to, due to 3个词的查询，发现如下：(examples are all from the dictionary)
1.Due to/owing to/because of/because +that...都可放在句首使用
eg: Due to/ Owing to the heavy traffic, he was late.
Because of his wife('s) being there, I said nothing about it.
2.Owing to/because of 在字典中有该条目的固定搭配，其整体作为一个prep.
而due to没有该独立条目，只是在解释due (adj.)词的时候提到第5个用法+to sth/sb= caused by/ because of
但是可以发现due当表语时，也可以+to sb/ to do sth，分别有不同的意思。
（1）due to sb 应支付，应给于，欠下
eg: Have they been paid the money due to them? 他们是否已经得到了应得的钱？
（2）due to do sth 约定，预期，预定
eg: His book is due to b published in October.他的书预定10月份出版。
纵上查询后，我再猜测下第二点：
由于due +to出现在任何文中，即使是使用在了be动词之后，也可以有很多种可能的意思，仍然要看上下文，所以，当看到due to的时候，如果能够用because of/ because that那最好选则用because,因为这样不容易产生歧义。
Due to means "cause by". It shoud only be used if it can be substituted with "caused by". It does not mean the same thing as "because of ",
Incorrect: The game was postponed due to rain.
Correct: The game was postponed because of rain.
Correct: The game's postponement was due to rain.
以后再遇到due to只要把它换成我们熟悉的caused by就清楚多了。
