VogonPoet Hmm that sucks.
Wonder if it could be windows defender or something hanging out in the background deciding to mess with it whenever it wants to.
Atleast for me it fixed it immediately after the 2nd install, so I feel like its either something get corrupted or blocked during the install or the installer is having problems with something
Ill shotgun a couple (some obvious so forgive me if you have tried it already) things, maybe I will mention something you haven't tried yet.
Downloading a new install file from the website
Reinstalling after a clean PC restart
Stopping any other background programs before installing (steam, discord, microsoft products)
Disabling any Antivirus / Malware things
Re-Installing it while there is already an installed copy
Re-Installing after first doing an Uninstall
Stopping any File Syncing Programs before Installing (One Drive, Google Drive)