Bacteria can cause many different types of odors. The system needs to be sterilized. Unfortunately I would suggest replacing all the filters, including membrane, so there is no change of re-contamination. www.softenerparts.com sells the sanitizing solution for this. You can use house hold bleach also.
1. Turn incoming water off
2. Open RO faucet and run all the water out of tank
3. Remove all the filters and membrane
4. Empty RO tank completely
5. Add 1/2 teaspoon to each filter housing, reinstall housings with NO filters
6. Turn the water back on until water comes out of RO faucet
7. Shut the RO faucet off
8. Let this sit for 10 minutes
9. Flush the system completely of any residual bleach
10. It helps to use latex gloves when installing filters to prevent contamination again
11. Re-install all filters
12. Flush 2 tanks of water at RO faucet
This is recommended each time you change filters. It is very easy to re-contaminate the system with just bacteria from your hands, so use the latex gloves and wash hands thoroughly before changing any filters.