I see you have marked an answer as correct, but I believe that is a partially answer as that error will not throw up all the time for every incorrect mapping.
To make it clear, let's say when you are defining a Field Map you need to select a field in the Target column and say for example I have mapped Category to Short Description, it will not thrown any error and it will map it across to Short Description field.
There can be error message which will come up when you are trying to map a field which are not of same Dictionary Type.
Which means in Source Field you are having it as a String and in Target you are trying to map this to a Different field Type say Boolean then it will not work
In short, Along with this for different scenario there can be different error message coming up and not just 1 specific highlighted above.
Hope this helps. Please mark the answer as correct/helpful based on impact.
Regards,
Shloke
