Since it's in your name and you didn't "use" the fiver in Massachusetts, you had no obligation to retitle it in that State, so no problem there.
Link to rules.
I see no reason why a buyer would hesitate- Title transfer is just paperwork, isn't it? I don't see anything about a required inspection or anything
at this MA. page...
You can also offer to go with them to the DMV to do the transfer- a practice I myself prefer anyway when selling a vehicle/trailer. I like to be ASSURED that such liabilities have been legally transferred out of my name before I see the last of them!
" Not every mind that wanders is lost. " With apologies to J.R.R. Tolkien