An easy way to check what files are being detected is checking the Windows upgrade logs located under: C:\$WINDOWS.~BT\Sources\Panther\ (hidden)
<Asset>
<PropertyList Type="Inventory">
<Property Name="AssetType" Value="File" />
<Property Name="BinFileVersion" Value="12.1.6608.6300" />
<Property Name="BinaryType" Value="pe32_i386" />
<Property Name="FileId" Value="0000399858fee05a4025fa4f4ad44e33ea6da3bb2b13" />
<Property Name="LongPathHash" Value="smc.exe|8c12408703a7db94" />
<Property Name="LowerCaseLongPath" Value="\\srvfiles\aplica\utils\sep12v1.6x64\program files\symantec\name\version\bin\smc.exe" />
<Property Name="ProgramId" Value="00065c4f4ca2072ca700bc4742b0f4411d4d00000904" />
<Property Name="Size" Value="0x00000000000453C8" />
</PropertyList>
<PropertyList Type="DataSource">
<Property Name="ApplicableTargetVersion" Value="RS3" Ordinal="1" />
<Property Name="SdbAppGuid" Value="{ed79c2a0-99e1-447f-af6e-817f64d770e9}" Ordinal="1" />
<Property Name="SdbAppName" Value="Symantec Endpoint Protection" Ordinal="1" />
<Property Name="SdbAppVendor" Value="Symantec" Ordinal="1" />
<Property Name="SdbBlockOverrideType" Value="SDB_UX_BLOCKTYPE_OVERRIDE_UPGRADE_UNTIL_UPDATE_BLOCK" Ordinal="1" />
<Property Name="SdbBlockType" Value="BlockUpgradeUntilUpdate" Ordinal="1" />
<Property Name="SdbEntryGuid" Value="{a458669e-f09a-462c-87ac-7ef5b31adbde}" Ordinal="1" />
</PropertyList>
<PropertyList Type="DecisionMaker">
<Property Name="ApplicableTargetVersion" Value="ALL" Ordinal="2" />
<Property Name="ApplicableTargetVersion" Value="RS3" Ordinal="1" />
<Property Name="DT_ALL_FIL_HardBlock" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_HardBlockUx" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_HasBlockOverride" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_InboxHardBlockUx" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_InboxSoftBlockUx" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_NeedsInstallPostUpgradeData" Value="TRUE" Ordinal="1" />
<Property Name="DT_ALL_FIL_NeedsNotifyPostUpgradeData" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_NeedsReinstallPostUpgradeData" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_NeedsReinstallPostUpgradeUxData" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_NeedsUninstallAction" Value="TRUE" Ordinal="1" />
<Property Name="DT_ALL_FIL_SoftBlock" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_SoftBlockUx" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_UnresolvedAvWarn" Value="FALSE" Ordinal="1" />
<Property Name="DT_ALL_FIL_UnresolvedReinstallWarn" Value="FALSE" Ordinal="1" />
<Property Name="DT_ANY_ALL_IncludeInTelemetryUnversioned" Value="FALSE" Ordinal="2" />
<Property Name="DT_ANY_ALL_IncludeInTelemetryVersioned" Value="TRUE" Ordinal="1" />
<Property Name="DT_ANY_FIL_BlockAlreadyInbox" Value="FALSE" Ordinal="1" />
<Property Name="DT_ANY_FIL_BlockUpgradeUxTables" Value="TRUE" Ordinal="1" />
<Property Name="DT_ANY_FIL_FixedByUninstall" Value="TRUE" Ordinal="1" />
<Property Name="DT_ANY_FMC_BlockingApplication" Value="TRUE" Ordinal="1" />
In this particular case Windows Update found this and some other SEP executables in this folder (all installation files). So the workaround was to remove the entire folder containing the SEP installation files or temporarily remove the mapped drive.