Exported MP3 files have no audio

I’ve been having a problem C8.5. I normally bounce the 16 channel mix from my Dangerous 2Bus to a stereo track in the project that later will be sent to the mastering house. I then export an MP3 to send to the client for mix approval. About 75% of the time when I export that stereo track as an MP3 the resulting file will be 4-6 MB and yet there is no audio. If I import into Wavelab I get two flat lines. I have tried everything. In some cases I will have maybe 3 or 4 mixes of the same project, i.e. bass up, vox up, etc. Of the resulting MP3’s, all bounced the identical way, maybe 2 of the 4 will have audio and 2 will be blank…this is very frustrating, especially since I am recording at 96K 32bit and I cannot play the 44.1 16bit file to check it so I have to close out Cubase open the file to find there is nothing there.

Anyone able to weigh in on this or had a similar problem?