There are a few causes of this.
1) Permissions.
You are using a different account to run Windows than the one you installed it under.
2) There's underlying disk problems.
Run chkdsk or use the tools, check disk for errors method. Hopefully there are none because if there are you better backup ALL your stuff ASAP!
3) Antivirus is kicking in and killing the installer.
This happens quite often. Try disabling real-time scanning temporarily while installing the program. Once completed, if successful, exclude the TRS2019 program .exe and folder along with your User data folder found in C:\users\%profile\app data\local\N3V Games\TRS19. The actual folder will begin with build.
On this note, we recommend putting the data in a better location and in particular on another hard drive, and one that has plenty of space.
I agree searching the forums is difficult. The easier way is to use Bing or Google.