In the simulation or in the device operation, during the initial phase alignment, SnkBusErr is asserted along with SnkBusErrStat, indicating DIP4 error and other error conditions. Once the core aligns (SnkOof=0), no SnkBusErr is seen.
These error conditions are expected during the phase alignment, and SnkBusErr should be ignored until the core completes the initial phase alignment, which is after PhaseAlingComplete="1."
This is fixed in SPI-4.2 v8.1 Core. SnkBusErr will no longer be asserted during clock-data alignment.