Makerbot Replicator 2 printing problems.

[XprintererX]

Trying to print miniatures I cançt finish the printing and after spending some days reading and trying different things finally I decided to register and ask for help.
I am using version 7.4 with PLA filament at 210C.


This is the result:





































As you can see sometimes the infill is not right in some parts while in others is perfect.
Sometimes it shift layers while in other prins it does it correctly.
The different pictures are for different configurations printing different parts.

Here you can find the stl files:
https://drive.google.com/folderview?id=0Byk39ARl2L7EeFFEbjU1Y19yZjg&usp=sha ring

Until now I tried:

- Clean and grease the axis.
- Change printing temperature.
- Modify moving/extruding speed.
- Use netfabb on the files.
- Modify the infill percentage.
- Clean the bed.
- Use more hairspray.

What am I missing?