Or, when did 'feral' go from /iː/ to /ɛ/?

In a conversation with colleagues today I used the word 'feral' - to describe a Carignan - and was brought up short, since all three of them (an Irishman in his late forties, a Dutchman of a similar age, and a teuchter in her late twenties) failed to recognise the word as I pronounced it.

(I should of course note for the record that my idiolect is often the cause of conversational hiatuses. Nevertheless.)

Their confusion was such that I doubted myself, and had resort to Chambers, which thankfully confirmed my pronunciation as being the established form. Or rather, the established form in 1983 when it was published, but that is neither here nor there.

I then consulted Oxford Online, which gave /ɛ/ as being the correct form.

My question, of course, is, when did the shift occur? And why haven't I noticed it before now?

My larger point, as you will perhaps already have inferred, is that it is very difficult to remain a committed descriptivist in the face of such wilful linguistic drift on the part of one's interlocutors.