Here is the full text for search engines:
Indexing engine unreachable. Inner exception: Error in deserializing body of reply message for operation 'SearchIndex VolumeStatus'.
Now that this is out of the way, it might be something similar to:
I'd suggest to do the same as they mention, try a DTrace of EVIndexVolumeProcessor and try to find the reason for it.
After finding the reason, there might be a workaround for it, or you'll already have some "ammunition" to send a support case towards Veritas ;)