For my first attempt I had the same problem with the planetary gear bearing; after printing, it was welded together and would not spin. I printed it in ABS, 100% fill, and a 100% flow rate.
For my second attempt, I switched to PLA, 25% fill, and an 80% flow rate. Much better and I ended up with a very free spinning planetary gear. No problems at all.
I think the trick was to reduce the plastic flow rate from 100 to 80%.