Error 0x8051004D

Value: -2142175155 | 0x8051004D | 2152792141

What does it mean ?

OPC_E_INVALID_RELATIONSHIP_TARGET_MODE  
The TargetMode attribute of a relationship does not conform to the rules specified in the OPC.
Value: 77 | 0x004D | 0b0000000001001101

Where does it come from ?

FACILITY_OPC  
Open Connectivity Service (Package Consumption)
Value: 81 | 0x051 | 0b01010001

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