It could be that Premiere is interpreting the fields incorrectly. Try checking the settings by selecting the clip in the project window and right-clicking and go to modify>interpret footage. Try changing the field order and see if that fixes it.
60i and 30i are two (confusing) names for the same thing: interlaced video with 29.97 frames per second and 59.94 fields per second.
You might get better answers to this question on the Premiere forum.
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