Hmmm - on our 4c4 system the item type is changeable on the item master. I would save if you never did anything with the part then table maintenance would be okay, but with your system having it greyed out I would not recommend that - unless you can test it all the way thru in a test system. Enough to make sure it does not cause any issues going forward.
My latest mantra - make sure you have latest stpapi patches and the latest session object. If on LN then please explore the option of using DAL2 functionality.
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