My recommendation is to wait. But that's just based on the information I have. Its in the final stages. If you start sending stuff in before it is adjudicated (additional evidence, duplicate evidence etc..) it could delay your claim. Sometimes the system auto generates a claim status, when in fact, the claim is much further along. The system sometimes has hiccups. I've been assigned claims to work before that say RFD (ready for decision), I quickly glance over it to see what i'm dealing with and notice that the entire claim is rated, the award has been processed and the veteran has been notified and probably received their first payment. I'm honestly not sure why it would keep going back and forth. That is part of the process before it gets to my desk and I'm not confident enough to give an opinion other than the known occasional hiccups. "Preparation for decision"...I"m going to assume this means "Ready for decision" I'm not sure if Ebenefits and the system at the RO use the same terminology, but when a claim is RFD, that means its in a queue waiting in line for a rater to work it. I'm not sure what the suspended letter is, but we do have a term we use, "suspense" which basically tells us when the claim should be moved on to the next step. If nothing happens in the system that automatically closes that suspense, then there will be an "alert" for us to check up on it.
For example: Claim is sent ready for decision with a suspense date of 2/14/17. 2/15/17 arrives and it hasn't been rated. The system sends an alert (hey, this claim was supposed to be moved on in the process by this date, what gives?) We see that somehow it slipped through the cracks and it is put on a priority list. However, if someone does work it before that suspense date, it automatically closes that date and creates another for the next step in the process (the majority of the time).
When was your claim filed? Is it an original claim?