It did not register "SIR" as a word.
The sliders were "TQSF", "KWRI", "RNIV". I found FIN, FIR, SIN, TIN. It rejected SIR.
The sliders were "TQSF", "KWRI", "RNIV". I found FIN, FIR, SIN, TIN. It rejected SIR.
This ambiguity could have been avoided if the solutions were unique.