Pronunciation of vowel in vague as [æ] instead of [eɪ]

I have a friend who pronounces the vowel in plague, vague, and bagel as [æ] instead of the standard [eɪ] (so plague rhymes with flag, for instance). Interestingly, he apparently can't tell the difference between the vowel sounds (i.e. even when I say [veɪɡ] and [væg] back-to-back, he can't tell me which pronunciation is the one he uses and which is the one I use).

I had at first assumed it was a regional pronunciation, but his wife is from the same relatively small (35k) town in western Michigan, and she uses the standard pronunciation.

Is this shift common in his region (or any other region, for that matter)? Is it otherwise explainable? Any insight would be appreciated.

This sounds similar to the problems that Chinese speakers have with /e/ and /æ/ (see for example here). Essentially because the sound is not used in their mother tongue, it is confused with a similar vowel sound, in both listening and speaking. It could be that their dialect is so ingrained that they have this problem themselves.

I come from Toronto, Canada, and a bunch of younger people around here do this. Some speakers only do bag and vague, but I've heard some speakers pronounce bag, vague, and egg all with the same vowel, a sort of (really jarring) intermediate sound between bag and beg.

Check out the pronunciation of vague used on this site for language learners:

http://pronuncian.com/Sounds/Default.aspx?sound=33+6

As a Brit, this completely threw me, and was the reason for me coming here and reading all your posts.

This is odd for me too. Somehow, for me, plague could take either the vowel of vague or of bag when a noun (I would use the "vague" vowel if placing emphasis on the word), but only the vowel of bag when used as a verb. The sounds are not merged for me, and I don't know where I picked this up. I'm from Rochester NY.