Error 0x80042933

Value: -2147210957 | 0x80042933 | 2147756339

What does it mean ?

VDS_E_VD_ALREADY_MERGING  
The virtual disk is already in the process of merging.
Value: 10547 | 0x2933 | 0b0010100100110011

Where does it come from ?

FACILITY_ITF  
COM/OLE Interface management. FACILITY_ITF is designated for user-defined error codes returned from interface methods
Value: 4 | 0x004 | 0b00000100

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