REPLACE CLIP option greyed out

[EricWillhelm]

Okay, so that's it. The 'Replace Clip' option is not working in a session, and is greyed out in the right-click menu. This session was opened from an OMF, so my first thought (upon looking at the Audio Files folder) was that the problem lied in the files all being .omf files. So I did a Save Copy In and chose to 'convert audio files to specified format'. So now the files are all genuine WAVs, but that didn't help either. Something is causing this feature to not function in this one session, and I don't know what it is. It still works fine in other sessions. Anyone?

This is PT12.5 HD on Mac running 10.10.5

Addendum: I have my next guess as to why. Thanks to the nature of OMF's, I'm noticing the stereo files I'm trying to replace are NOT interleaved, while the ones I'm trying to replace them with ARE.