HDR alignment not successful

[CliveH]

I have tried to do an HDR merge on three Raw files and while the merge was successful, the image is soft because the alignment isn't quite right.  I tried both the Perspective and the Scale, rotate and translate options but both gave a similar result.

 

I have tried other images which merge successfully so the problem appears to be specific to this image.  It is of a hillside, photographed from across a lake - the hillside is relatively low in contrast while the surface of the water has better definition and I wonder if the problem is that the auto-alignment is trying to align the higher contrast water surface (which is moving slightly between the shots) rather than working off the lower contrast (but immobile) hillside. 

 

I would just put this down to it being a difficult image except that a merge in Lightroom 6.7 worked fine.  I suspect it isn't a bug as such in the Beta but something that would be common to the Mac version as well (although I can't test this). 

 

Hopefully there will be some scope to improve the alignment algorithm.  If not, would it be possible to add an option to manually align the images?

 

I can provide copies of the Raw files if it would help.  In the meantime, I am attaching a jpeg of the middle shot in the bracket for info (the upload has just given an error message so not sure if it's worked or not).  (Note - I realise that an HDR merge may not be required to bring out all the detail but as I took a bracketed set I thought I should use it.)