I replicated this scenario is couple of servers, so you should be able to replicate at your end as well.
Step1. Clear the browser cache, load the FIori launchpad and keep the Network tab (in F12) open.
Step2. On the Launchpad, moment any tile loads and becomes clickable, click on it to open it. (I would say this is what a normal end user would do.)
You have to be quick on this step.
Now Chrome will freeze for 20 seconds.
If you carefully see the network tab, this is what actually happens in background. (see here)
When you load the launchpad, even though launchpad becomes clickable, one of the bigger library file ext-core.js (compressed size of 1.2MB) keeps downloading in the background. If you click on any tile before this download completes, then the app makes another call to ext-core.js, since this file is not yet available in cache. (we did not let it complete download). Now that Chrome sees two calls for the same request, it implements a 20s timeout before issuing the second call.
Anyone see this as a issue? and has any ideas to overcome htis stall?