Accents and Semitic words

My last message, musing on the accentuation of σαβαχθανι in Matthew 27:46, has caused me to reflect further and in fact brought me to a point of consternation in regard to the following question:

What is the rationale that editors of the Greek New Testament use to put accents on Semitic words?

In my folly I had previously assumed that editors placed accents on the stressed Semitic syllable, or, with Rahlfs, omitted accents on such words entirely. This works for a great many words, but there are many examples that do not fit this pattern. For instance Βηθλεεμ is given by many editors as accented on the last syllable, though in the Hebrew the stress is on the penultimate syllable.

Why does NA26 put the accent on the last syllable of Zerubabel in Matthew 1:13, but WH on the penultimate?

Why does Scholz (1830) put the accent on the first syllable of Αχαζ in Matthew 1:10 while NA25/26 put it on the final syllable? (Other editions could have been consulted.)

Are editors generally just copying from each other rather than thinking through the principles involved in accentuation or is there a pattern of treatment found within Greek mss?