Dear @Rims
My apologies for ceasing to reply. Unfortunately, I got very busy before the holidays and ended up forgetting about it completely after I came back to work.
Curtis made a good point about minimal reproducible examples (i.e., making the smallest app you can, that raises the same issue) as the best tools to diagnose issues, but also to help others help you.
In particular, you gave a link to you app without giving a link to your source code, which is in itself is already a major barrier for people who would like to help you. Many errors cannot be guessed only from the error message without having access to the underlying code.
That said, even better than sharing the whole code of a specific application (which would require the person to get familiar with a lot of domain-specific code irrelevant to the issue), minimal reproducible examples provide only the source code of the problem (usually with some accompanying code to generate dummy data with having to download anything) which helps the person rapidly focus on the source of your problem.
It might sound like more work, but I can guarantee that it gets you more and quicker replies. See https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example for more information.
Furthermore, more often than not, writing that minimal example is all that's needed to identify the problem yourself, which is an even more satisfying feeling.
With all that said, I've just had a look at the app in Chrome and it seems to work fine now. So either you fixed it, or there were independent updates in R packages or Chrome that solved it.
Best wishes
Kevin