I assume that you don't make use of any custom JavaScript function that would apply this reversal ;-)
I can't remember that we and none of our customers ever experienced this behavior, regarless the version.
You said "on some fields". Does this mean that "other Fields" don't show this behavior? Have you determined any shared characteristic of all those which work, against all those which do not? (per instance: those which have numeric values fail, whereas those which have alphabetical characters won't?).
Also, you said "Fields". Does this mean that the behavior is really related to Fields, but not to Content Objects? To sort this out, I would simply edit the rule of a "wrong" Content Object, changing its related (wrong) FIeld against another Field that proved being OK in another Content Object; if the wrong behavior stops, then it's indeed related to the Field; if the trouble persiste, then it's more related to the Content Object, or its tag in the InDesign document (per example - you never know - a text that would be set in Arabic or Hebrew??).
If you really suspect that the trouble is related to the data, then you could investigate a bit more with the "ReportMessage" QLingo function, which- as its name may indicate - would add messages in the uCreate popup, at the end of a print production; so, consider coding something like
ReportMessage("My suspected field value=" & |->[myField]) |->[myField]
Again, if the ReportMessage outputs correct values, I would investigate the document.