Thanks for posting to the community forum! The issue does not appear to be caused by the VCO not functioning appropriately, but it appears to be an issue with IFrames, itself. This is not something that we can comment on directly, however, there are several pages regarding the development for Facebook applications, and messenger applications that discuss the issue and a way around the security limitations. You can find information about this issue if you do a Google search, and specifically looking for sites that specifically relate to the development for Facebook.
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