Another related improvement:
Issue 1740 – Start main window with the last user local folder instead of always starting in Documents folder

Thanks for your report.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.

I've just seen the earlier thread about this issue here - missed because I didn't search for "lunch" !
I've tried the clean re-install and the alternative user (roaming profile corruption) options suggested, neither worked and in both cases process monitor demonstrated the same multiple UNC interaction behaviour. I'm happy to run a debug version of 5.15 if supplied, or a log if useful (although currently I've downgraded back to 5.13.7)

Windows 7 Build 7601 SP1

Since upgrading from WinSCP 5.13.7 to WinSCP 5.15 the program is exceedingly slow to launch (5+ minutes). An exploratory with Process Monitor is indicating that the new version is attempting to poll (or otherwise interact with) several thousand potential UNC network locations, all of which are access denied. Although each interaction is subsecond, the cumulative effect prevents WinSCP launching in a timely fashion.