P: Unable to merge the photos. Please cancel and review your selection.

Ha, God knows! They are reading these posts and have made some improvements to merging in recent releases so there's always hope. In the meantime, try playing around with the different levels of deghosting. Low might work best. 

Hi Jerry, You are right. Noise problem gone, but now I have a ghosting problem. Is there hope that LR will be improved in this matter in the near future?

Hi Christopher. Maybe you have deghosting on. It's not the best feature of the HDR merge but I've seen this noise you're referring to before and it was when I forgot to switch it off when I didn't need it. Switch deghosting off and try again.

Rikki - Got a new one for you. In Lightroom, when I HDR some bracketed images, the results come out with patches of excessive noise. Have no idea why and I have to resort back to using Nik Efex Pro 2. Here is a Dropbox link to view 1) The 6 dng images, 2) the resulting HDR dng where patch noise is visible,  3) the final jpg image that was made with Nik .  https://www.dropbox.com/s/xgwd57e7w13l760/Noise.zip?dl=0
Tx, Christopher

Delighted. After spending $5000 on the lens, I can now get its full use again.
tx
Christopher

Will do. Many thanks upfront

The news is.... this should be fixed in 10.5 released today. Give it a spin and let us know if you have further issues. 

been 2 month now. Any news yet

Once the engineers have made a fix and it is live, we will respond on this thread. I don't have an ETA I can share with you. 

This is what i am told, but need to thank you for your time and for caring........ The engineers identified the issue and have logged a bug for it. Thanks for reporting and providing sample files.