It's not clear why PA is handling the two sales from two separate state returns differently. The good news, as a PA resident, is that the tax doesn't change no matter where it is reported. PA has a straight tax liability on all taxable income (3.07%) so it won't change no matter where the income is reported.
As long as you are seeing credit for taxes paid to another state for both ME and RI your end results will be accurate.
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