same issue here with r240 in both 32 and 64 version. Tried to trace. When Construct2 calls the minifier this will end up like that in my case:
C:\Users\M>java -jar "C:\Program Files\Construct 2\exporters\html5\tools\closure\compiler.jar" --js "D:\Projekte\Construct 2\2016\Notenmeister\HTML\c2runtime_tmp.js" --js_output_file "D:\Projekte\Construct 2\2016\Notenmeister\HTML\c2runtime_min.js" --language_in ECMASCRIPT5_STRICT --compilation_level ADVANCED_OPTIMIZATIONS --externs "C:\Program Files\Construct 2\exporters\html5\jquery-externs.js" --externs "C:\Program Files\Construct 2\exporters\html5\c2-externs.js"
D:\Projekte\Construct 2\2016\Notenmeister\HTML\c2runtime_tmp.js:19285: ERROR - this language feature is only supported in es6 mode: let declarations. Use --language_in=ECMASCRIPT6 or ECMASCRIPT6_STRICT to enable ES6 features.
let browserInstance = null;
^
1 error(s), 0 warning(s)
May be there are new features not supported by the minifier?