Hey,
It seems that this takes a bit longer than it used to/should. I haven't tested extensively in prior versions yet but I don't remember things taking this long before.
When it gets stuck like that it eventually completes but it might be taking hours (i haven't clocked it exactly)
I'm currently on latest 1.6.3 pre release build.
I've sent a test project to you via email to support@agisoft.com. To reproduce please decimate the provided model down to 50 000 000 or 40 000 000 and then try to do a gradual selection on it (Model before decimation shouldn't get stuck on the Analyzing step. I kept the original though so you can see what's going on)