Hi Carson,
Upgrading my docker image to use R 3.6 and the latest versions of RStudio-server and shiny-server did not fix the problem. Also, I was able to remove almost all extraneous code and preserve the discrepancy, i.e. I have a "minimal reproducible example" of the problem.
Minimal in the sense that the shiny app is quite trivial. The docker image is fairly big.
Since you are at RStudio can I send you the Dockerfiles and the app files?
Please let me know the best way to proceed.
Thanks