When creating proxies some files won't transfer to Media Encoder

I have imported a bunch of clips in Premiere selected all of them and selected the "create proxy" option and then selected an ingest preset. 

As usual all the files were ingested in Adobe Media Encoder. However when Media Encoder finished the job I realized it had missed a few clips. I thought it might have slipped through and reselected only those clips to make proxies. However when I would click OK on the premiere window "create proxies" they would never show up on Adobe Encoder. I tried re exporting some of the files that actually Encoder was able to create proxys for an they re exported fine. It seems that for some reason Encoder is not able to make proxies for those files. Does anyone here have any leads on how to solve this?

Thanks!