Managed Policies with active assigned computers where the Inventory Rule is the default Software Resource Keys generate a new Detection Rule every 2 hours, beginning to fill up the Item table.
This usually shows up by running the SMPDiag when checking for large amount of entries in the Item table of certain types. When detection checks show up as being duplicated many, many times, this issue is occurring (or a variation on this issue).
A point-fix has been created for this issue on version 7.6 HF2.