This is a feature not a bug. In FC 8.4 the drill bit will go into the PCB with G1 speed (with the set feedrate), reach the drill depth and then go up to the travel Z again with G1 speed. Slow, all over was only G1. In FC 8.5, in order to make the drill process faster, the order is like this: drill bit enter into the material with G1 speed (with the set feedrate), reach the drill depth, return to zero again with G1 speed but after that it will go up to travel Z with G0 speed (fastest speed the CNC system allow). G1 Z0 is exactly the command that it's telling the CNC router to move to Z=0 (top of material, with speed G1). At that time we discussed this, I for one was for getting out of the hole as fast as possible to minimize the time, to minimize the drill usage (the temperature is very high at high speeds in the hole and the resin is melting creating drag and usage on the drill bit). But JP decided it is safer to reach the top of material from the drill depth, with speed G1 (set feedrate). To be honest, for drill bits under 0.6mm I breaked a few due of the G0 high exit speed. So in the end we settled for this. Conclusion: the drilling process is much faster now.