Engage issues occurring after publishing WBT

I am having an issue with Engage slides after publishing my WBT. The WBT is about 135 slides long and contains both Quizzes and Engage Interactions. The problem occurs on the Engage slides. I cannot pinpoint the issue because it is not consistent. Some Engage files will work fine and others just give me the blank screen. When I check the files and re-publish, they seem to be fine but then other Engage files are blank. It is driving me crazy. I have tried Web, LMS, etc. The issue doesn't seem to occur when I publish the WBT in Modular (smaller) increments but the customer is adamant that the final product is one file.

I have tried saving the PPT as Powerpoint Presentation and also as Powerpoint 97-2003.

Any ideas? I appreciate your assistance.