Proposed Mechanism

The carbonyl group of ester takes an electron and converts to the radical anion which takes a proton from the alcohol and forms the radical intermediate. The latter takes the second electron and a proton and undergoes elimination of an alcohol to give aldehydes that further proceeds further reduction to give the desired alcohol.

Examples:

L. A. Paquette, N. A. Nelson, J. Org. Chem. 1962, 27, 2272.

R. H. Manske, Org. Synth. CV2, 154.