Occasionally, a lead or contact record will "disappear" from the search results.  That is, searching by name or any other info will yield zero search results.  The record is still there when browsing through the list of records, or when accessing it directly via the url (with the correct contact id or lead id).  Re-saving the record will sometimes fix the issue (assuming the record can even be found in the first place).

We have also started experiencing problems with missing records retrieved via the api.  We sync the records by retrieving records, i.e. lastModifiedTime after a certain date.  Sometimes these api calls unexpectedly skip records that are after the lastModifiedTime but before other records retrieved in the result set. 

The two problems are probably related, i.e., the records disappear from both the search results in Zoho and from the records retrieved via the api.  It seems to happen randomly, and it's hard to reproduce, but it has happened many times over the past couple of weeks.  This system has been running stable for years, and this just started happening, so I'm wondering if you guys pushed some production code recently or introduced some kind of database replication on your end that are causing things to get out of sync.

In any event, it's a really serious issue, because we are randomly missing data, and if it doesn't correctly sync the first time, it never will (because subsequent syncs will retrieve records with later modified dates, and we sync based on the latest modified date).