yes,
a bug i think, on build before 30623.
Update 0.53 build 30623
"The FINDSET function may return an incomplete record set, depending on the size of the caching Record Set configuration setting in the Microsoft Dynamics NAV client that uses the Microsoft SQL Server database"
Platform updates overview - 3.70.B - NAV2009 SP1 (UPDATED 5)
dynamicsuser.net/.../platform-updates-overview-3-70-b-nav2009-sp1-updated-5.aspx