Hi Juan, I do appreciate your efforts to unravel issues in a very complex piece of software. I see where you placed ucrtbase.dll in Bin directory. Ucrtbase.dll was supposedly taken care of by a Microsoft 2015 Windows update which was done on my PC.
After the recent updates, prior to the last one, I lost the PI icon on my XISF file types. The latest update fixed that after uninstalling and reinstalling PI.
As to my first issue, I assume most people use the default Process Explorer launch which is Special GUI Effects/Animate Autohide Windows checked. I have always used this default in V1.8.4, and the first time I unchecked this option is with 1.8.5 and that was when this problem showed up for me. The issue is still 100% repeatable so that when I click the Windows X to shut the program down, Pixinsight is still running in Task Manager and till I manually shut it down, I am unable to relaunch PI. Again, I can easily either check the animate GUI option or use File/Exit to leave the program so it's not a big deal for me.