Using ExifTool to remove all previews deom DNG file?

[jls3512]

I'm using exiftool to switch the red and blue channels by changing the Color Filter Array... this has been working pretty well,  however I'm having one small issue.. and that is the built in previews are based off the original CFA pattern, and sometimes while I'm working with the files in lightroom, they suddenly revert back to the wrong preview, and the colors are wrong (for what I'm doing) 

I'm wondering if I can use ExifTool to remove all the jpeg preview and embedded jpeg images of any kind from a DNG file, so when I get back to lightroom it will be forced to re-build the preview data.   the problem I am having is even though I tell it to discard and re-build the previews, it ends up telling me previews already exist, so it doesn't re-build them... most of the time my images will look the way I want to, but once in a while, I'll open one up and try to work on it, and as soon as I touch one control, it pops back to the original color.. but if I zoom in on it, it's the way it was after I changed the cfa pattern, it's weird, but I'm sure it has to do with the embedded jpeg previews

I'm not sure if this kind of thing is within the scope of ExifTool, but I thought I would ask, it seems like a lot of people here have a LOT more experience with this kind of thing, and I really appreciate the help!

[Phil Harvey]

To completely remove the preview from a DNG would require a re-structuring of the file that ExifTool is not willing to do.

- Phil

[jls3512]

I learned how to re-build the jpg previews with lightroom 5.. just thought I would post how to do it here in case someone comes across this post using a search who has the same problem.

I was discarding and rebuilding the wrong previews...  To update the jpeg preview with lightroom 5 just go to Metadata > Update DNG Preview & Metadata.. I just couldn't find it because it's not with all the other preview building options under Library > Previews