The arc at the end of the profile sounds like a classic cutter comp error.
Are you sure you remembered to cancel cutter comp (back to OFF, i.e. G40) as soon as you reached the end of the profile, before going off for another pass (depth repeat) or off to a tool change or another feature?
You should have comp ON (LEFT or RIGHT) and an appropriate lead-in move at the beginning of your profile, and comp OFF followed by an appropriate lead-out move at the end. You should include these things in the range of blocks you repeat with the depth repeat.
Regarding the speed Z comes down at: what is the plunge rate you gave in your depth repeat operation? Was the first move you included in the depth repeat a feedrate move, or a Rapid? Is the series of moves you are repeating a closed circuit (ends back where it started)?