We have three of these lathes, all built around 1999/2000. They are all 840D Siemens components. I've had to replace or repair a few drives over the years but there was never a problem finding replacements. The weak link is the Duplomatic Turret. The main cam wheel and rollers will eventually wear out and the turret will have problems locking up. At first it's intermittent and then it gets progressively worse. the first alarm code you get is an overheated turret motor which leads you down the wrong path (ask me how I know). Macoser is the dealer for Duplomatic in the US and they stock all the parts. They will also rebuild your turret for about 10K. I have rebuilt the turret in each machine and can do it for about $2500 in parts.
If you inspect the machine, Have the operator do a lot of tool changes to see if there is a problem.