Groovydoc will add timestamps to the HTML file it produces. https://sources.debian.net/src/groovy/latest/src/main/org/codehaus/groovy/tools/groovydoc/gstringTemplates/topLevel/index-all.html/#L19
Files were built with different encoding (non-UTF-8 vs. UTF-8).
Our notes about issues affecting packages are stored in notes.git and are targeted at packages in Debian in 'unstable/amd64' (unless they say otherwise).