I've not played this piece (very nice music), but the published fingering in measures 14-17 has to be some kind of typo if the phrasing is to be smooth.
I'm a fan of using the easiest fingering as well as the same fingering as much as possible for similar passages, so I would continue fingering the first R.H. Ab in measure 14 with 4, but instead use 2/3 on D/F, switching finger 3 with finger 4 (or 3-5, whichever feels most secure to you) as quickly as possible. That leaves 1,2,3 free to smoothly play the lower F,Bb,D while 4 (or 5) holds the upper F. Measure 15 would be handled the same way, the switch being only slightly more difficult. The Andante tempo should easily allow for plenty of time to accomplish the proposed finger substitutions.
Hope this helps.