Reduction of conjugated double bond by sodium borohydride
Scifinder shows lots of reactions such as you describe. Often (but not always) copper is used to help favour the 1,4-addition (alkene reduction) process.



The simplest example I can see is the reduction of 3-penten-2-one[[2]] - when treated with NaBH4 the majority (89%) is reduced at the ketone only, while 11% of the doubly-reduced product is formed:



Obviously different substrates would give different product ratios, but certainly this is a plausible (and precedented) reaction.