Targer drive not ready.

"Target overflow" just means that the disc being used to make the copy doesn't match in size. "4.7GB" to the master disc. Sometimes this occurs when you make a mistake thinking the disc in the copy slot is a DVD blank but it may be a CD-R blank(by accident) or sometimes the Master disc is a BD-R and trying to copy to a regular DVD-R (won't fit)

"Source drive not ready" is when the Master disc keeps spinning in the attempt to read. The "culprit" alot of times is the brand, or scratched, dirty, corrupted discs.
Make a copy of the master again (if possible and on your PC with a different brand of disc) then use the new Master to make the multi-discs you want.

"Target drive not ready"
is when a disc with information already on it, is in the copier (can't copy over it) sometimes we make mistakes and put the Master in the copier and vice versa : )
or no disc in it at all, and or some sort of incompatible blank media.

I have a 7 disc duplicator by Pioneer and I found that in the last few years since I've had it (since 2005)
I ran into the above situations alot.
I use it as a standalone (not hooked up to any PC etc)

It still works great but I find that was having a brand name issue with the discs; certain discs that it used to read in the Master/Source drive like Taiyo Yuden, Memorex, Ridata, SKMAX, and Phillips, suddenly don't want to read properly when inserted. The discs keeps spinning and then when you press "copy" it says "Target overflow" or "Source drive not ready" I found that solution I mentioned above with the changing of the disc brand helps fix the situation. I didn't want to hurt my brain trying to figure out what it could be as I use my duplicator for business and time is money.

Through trial and error I end up just making duplicates from my PC on different brands (cheaper unknown brands work fine) and then using the "new master" made from these is the only way I can duplicate..weird!

P.S sometimes the lens may need an old fashioned cleaning with a lens cleaner or Dust blower.

Once in a while one or two of the doors get stuck even when all 7 discs are completed...just take a q-tip with vaseline and put it on the track wheel for some lubrication and the door will open up easier.
Just some tips from someone who's had their player a long time

Hope this helps anyone in need out : )

I know I get the same error when I try to copy a cd and I accidentely leave a dvd in one of the target drives. So make sure that when you copy a cd that you have cd-r's in the drive and when you copy dvd's that you have dvd'-r's in the drives. Or it could be something else. Just a thought.