3663380 - Environment variable SNC_LIB resets or doesn't have the expected effect

When trying to connect to a system via SAP GUI, below errors appear:

• SAP Logon popup:
  Security Network Layer (SNC) error (location <applicationServerInstance-W##>)
  and
  
• Work Process trace file (number indicated by "W##" in the location above):
  *** ERROR => SncPFrameIn(): Peer's SNC library is non-interoperable with ours!
    Peer SNC-Adapter = "<SNC-Adapter A>"
    Our  SNC-Adapter = "<SNC-Adapter B>]
  <<- ERROR: SncProcessInput()==SNCERR_INCOMPAT_MECH

Which normally would indicate a mismatch of SNC libraries between server and client workstation.

However:

• When checking values for parameter snc/gssapi_lib on server side and environment variable SNC_LIB on client side (via command line: SET SNC), they are already using the same SNC library.
• SNC library shown on environment variable SNC_LIB is different from the Peer SNC-Adapter shown in the Work Process trace file.
• When rebooting the system, SNC_LIB resets to the same SNC library shown in the Work Process trace file.

• SAP NetWeaver
• ABAP platform

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