When you click in the mint or printer field and start typing it selects one of the mints or printers. When you click off the field it keeps that one selected. On multiple occasion I didn't actively select a mint/printer, but it used the one that was highlighted. Even if you press esc on the keyboard without selecting it doesn't deselect the chosen one.
The behaviour should be that you should explicitly select the mint/printer you want and then it populates the field. Otherwise erroneous data is accidently being selected.