Clarification of a שוא נע rule

As the Shabbos before my mother's yahrtzeit, I will lain this הפטרה from time to time. In 2014 was actually my first time laining הפטרת במדבר. (It did fall out this way three years prior but there was a בר מצוה in shul.) I came across something I thought odd and eventually discovered an interesting nuance of which I was not previously aware. Going through my other stuff on במדבר it appears Elie's post addresses almost the exact same issue. But I found it a little difficult to follow (probably my fault, not his) and so I thought I'd lay out in simpler English:

There are a number of reasons a שוא would be נע. There is a well-known mnemonic - א ב ג ד ה ו where each letter stands for a different rule. The ג stands for תנועה גדולה. If the שוא is preceded by a קמץ, for example (except if it's a קמץ קטן,) the שוא should be נע. However, I recalled that there is an exception to this rule. If the letter with the קמץ has a trop on it, it does not make the שוא נע. I was therefore puzzled when I saw in my תיקון:

  וְעָ֤נְתָה שָּׁ֙מָּה֙ כִּימֵ֣י נְעוּרֶ֔יהָ

The שוא under the נ of וענתה was shown to be נע. But what about the note on the ע?

I have the big monster of a תיקון סימנים which has a thorough discussion of the rules in the front. He goes into detail about this exception. Indeed, there is an exception to the exception. Not surprising in the world of דקדוק*. The trop only prevents the שוא נע if it is in its natural position. If the word were on its own, where would the note be? We see from דברים כ"ה:ט וְעָֽנְתָה֙ וְאָ֣מְרָ֔ה  that the natural accent is מלרע. In our case, it is pushed forward by the מלעיל accent on שמה and the rule of נסוג אחור. Since the מהפך on the נ is not its natural position, the שוא remains נע, just as it does in בראשית ל:ל"ג וְעָֽנְתָה־בִּ֤י צִדְקָתִי֙.

* I recently heard a great quote from R' Yaakov Kamenetsky: "In דקדוק, there are no exceptions. There are simply more rules."