Import mess up

I am using LR 6.14

Today something went wrong during 'import' and I ended up with 3 copies of every file.

OK I thought simple solution delete them all in LR, and reimport from originals - the problem is it won't re-import the files.

I thought OK .. I create a new folder put copies of originals in there - and re-import from that folder.

Initially, it looks fine I browse to it (in Import module) all pics show, all ticked and then after about 2-3 sec they all disappear and nothing to import.

How can I force re-import of these file ?