Type an "i" and it could well be replaced by an uppercase A followed by a symbol. Apple has posted a support document advising that a future software update, likely iOS 11.1.1, will correct the problem.
These fixes aren't flawless but they'll do the trick until Apple issues an update to A [?] OS 11.1. The company suggests going into Settings General Keyboard Text Replacement, the tapping the plus sign to add an entry. Hit the + button, and in the phrase option type "I" plus "i" in the shortcut option box. The bandaid lets users replace a capital "I" with a lowercase "i" - which will look odd, but not as odd as the weird exclamation point-question mark combo. It involves setting up a text replacement.
Users can also disable predictive text completely, in order to halt the autocorrection.
The Apple iOS 11.1 was recently released as an update, advertised as Apple's first milestone upgrade.
It seems to affect iMessage, as well as other apps including Instagram and Twitter. Which, judging by the fact that "I" is a relatively important letter in the English language, will probably be sooner than later. The switch has impacted users on iOS 10 and 11.
The BBC has contacted Apple for comment.
The glitch arrived with iOS11.1, which was released last week, bringing with it hundreds of new emojis.