I have spent a few hours now trying to load a file in ISO-8859-1 encoding (my project is all UTF-8, but a few files need to be in ISO-8859-1 because of a tool I use that can't handle UTF-8 well), but IntelliJ is constantly opening it in UTF-8, then it complains ("File was loaded in the wrong encoding") and offers to "Reload in another encoding"; however, the reload seems to have no effect.
I found that this is a very old (2.5 years) bug, reported as https://youtrack.jetbrains.com/issue/IDEA-124495, and I can't believe that it has not been fixed. I am ending up starting eclipse just to edit these few files, which is a real pain. Considering how good IntelliJ is in almost every respect, I think this bug is profoundly unworthy of Jetbrains.
Can we expect a fix for this bug any time soon? Otherwise, I would suggest you take out the "Reload in another encoding" option, because it is making a promise it cannot hold!