No. Starting from my now-4.26 version, I made a backup copy of WinSCP.ini outside the WinSCP directory. Then I over/reinstalled the older 4.25 (WinSCP.ini still present). Then I over/resintalled the 4.26 (WinSCP.ini still present).
Neither I was able to reproduce the problem. If it ever happens again, please let me know.