Recently it appears that another autocorrect bug was discovered in iOS 11 not too long after the first one, which was found earlier this month. Apple is aware of the issue, thankfully, and have since offered up a temporary workaround (via AppleInsider). Like we said, it is temporary and hopefully a proper fix is on its way.
Basically what Apple is asking users affected by this bug to do is to reset their keyboard’s dictionary. This can be done by going to your Settings > General > Reset > Reset Keyboard Dictionary. After that you have to reboot your device and it should be back to normal, at least that’s what some are claiming.
Here's what worked for me (from Apple): reset Keyboard Dictionary. To do this, navigate to Settings > General > Reset > Reset Keyboard Dictionary. reboot the device then test to see if the issue persist.
— Jim McCarthy (@goldstarjim) November 27, 2017
The fix seems to be a mixed bag where some are claiming that they have had success with it, while some claim that this does nothing for them, so your mileage may vary, but hopefully you fall into the former camp. We can only assume that a proper fix will arrive in a future update, but when exactly remains to be seen.
It is rather disappointing that iOS 11 seems to be riddled with bugs that appear to be rather simple, and ones that Apple should have caught well early on into development, but either way for those afflicted, we guess you’ll have to wait for the proper fix.