I ran into the same problem as Alessandro. HSH...no problem. PTM gave me an error at the final processing stage. Images were taken with a Nikon D800 at 7360 X 4912 pixels (36mp).Processing was done under Windows 10 with 64gb of memory.
Per Dave’s recommended procedure above, I set up a fresh download of builder and the fitter on the C Drive. Pulled in the fish fossil sample set...that processed no problem. I then took my file set reduced the image size to match the fish fossil test set (2000 pixels on the long edge). Worked fine. So I started increasing the file size.
To make a long story short, I ended up, removing the metadata, processing the full file size image, and then cropping the image at the end. I was able to successfully perform a PTM run with an image file cropped up to 29.19 megapixels. If I cropped to 29.21 megapixels or more it would fail, so it appears that there is a size limit on the PTM processor.
Alessandro is working with a much smaller image size but only 8gb of memory , but I would think that that should be enough. I would recommend removing the metadata from the files, and then testing. Not sure what effect that will have but it seemed to make my files process more smoothly. Try different cropped sizes and see how far you can go before it fails. You can then size your images accordingly.
I read a comment by Carla in another post that indicated that apple computers don't seem to have a problem. An associate of mine is going to try and see what happens.
Hope this helps