Using replacement fields to pipe in answers to previous questions generally works fine if you create the question and use the "insert replacement field" button and then make no subsequent changes to the question, however, strange things sometimes happen when you try to do any of the following.
1) Manually edit the value of the replacement field to try to refer to another field. Example: manually changing {INSERTANS:69317X342X2886} to {INSERTANS:69317X342X2887} in the question text
2) deleting the replacement field code (e.g. the "{INSERTANS:69317X342X2886}") and replacing it with another.
3) Copying a question with replacement fields and attempting to modify the replacement field in any way

"Strange things" in this context basically means changes between what the editor shows before and after you hit the "update question" button, which might include any of the following
1) ignoring the change you just made
2) Instead of replacing the old replacement field with the new, both appear
For example

If I started with this question:

"How did you first meet {INSERTANS:69317X342X2886}?"

and I deleted the replacement field and replaced it (using the button) with this: {INSERTANS:69317X342X2886) so that the question text looks like this:

"How did you first meet {INSERTANS:69317X342X2887}?"

then I hit the update question button and what I just wrote changes to this:

"How did you first meet {INSERTANS:69317X342X2886}{INSERTANS:69317X342X2887}?"

Sometimes trying to delete the second INSTERANS just makes things worse and gives me this:

"How did you first meet {INSERTANS:69317X342X2886}{INSERTANS:69317X342X2887}{INSERTANS:69317X342X2887}?"

This behavior does not appear to be consistent.