I have two main questions, followed by some bonus questions.
1) The pronunciation of the word "זכר" in Parshas Zachor
Why do many Ashkenazic congregations repeat (at least a portion of) the last verse (Devarim 25:19) of Parashat Zachor twice, once saying "zeikher" and the other "zekher" (flipping the first vowel from tzeirei to segol)?
2) The pronunciation of the words "ולהרוג" & "ל/פניהם" in Megillas Esther
Why do many such congregations have a similar practice for two words in the Scroll of Esther, in verse 8:11 ("v'laharog" / "laharog") and verse 9:2 ("lifneihem" / "bifneihem")?
bonus questions:
- How did these doubts regarding the correct versions arise, and why do Sefardim and Teimanim not seem to have such doubts?
- What are the arguments for and against repeating these words?
- For those that do repeat the words, does it matter which version is said first?
- To what extent do these issues affect the validity of the performance of the mitzvot to hear these readings?