It wasn't a
theory at least at my end- I used
procmon to confirm the behaviour. All packs behaved exactly the same way. I had to install each pack individually. I ending up installing one pack twice, I probably aborted it prematurely first time around.
What happens in my instance is that it downloads the updates to the D drive from the internet (as set in my CCC). So try setting your downloaded updates to another drive to see if you behaviour changes (and try it on the same drive as the ultimate destination). It then copies and extracts a RAR achive to a temp drive in the user account area, on the C drive. All throughout we get progress bars. Once done it then moves these extracted files to the D drive where they belong (yup from D drive to C drive and then back to D!), this does not show a progress bar, rather an orange animation scrolling left to right where the progress bar is. Finally it states it is complete.
> After reaching the end of the progress bar, it took under 2 seconds to return to the "click here to continue" screen. This is where you get the "animated" orange progress bar that scrolls from left to right. For you it took 2 seconds, for me it took an hour at least with one of the packs, hence no issue for you. Again I know this is a stage where files gets moved from the C drive to the D drive - I used procman to confirm it and watched the files get moved from the temp folder to the destination with my own eyes.