A sharp high G note is a common problem. It may simply be that the reed is just dry and needs to take on some moisture. Blow some air through the reed for about 30 seconds. If a lack of moisture was the problem, this will fix it. If it doesn’t, then you must look further.
Note that taping a high G hole close to halfway across the hole may cause squealing. If the tape is ok then check the mouth size. If the mouth is too small, use the mandrel or reed poker to open it a bit. This will bring the overall pitch down but will especially flatten the high G in relation to the other notes. If the mouth is a good size, then the blades will need to be thinned by scraping with a sharp blade.