The download and extraction succeed. Validation succeeds. Then the install fails at "Checking the downloaded runtime" with a message telling you to check disk space and directory access, and there is nothing wrong with either. This is pingdotgg/t3code#18551, fixed in PR #18472.
Why it happens
The validation step runs the runtime from a disposable temporary profile. That runtime is itself a launcher, and its children - a PyInstaller-packaged process here - keep handles on the executable and the unpacked DLLs. Closing the validation wrapper does not wait for those children to exit, so when the installer removes the temporary directory the removal fails with EBUSY or EPERM. The run is marked failed and the error blames the disk.
Windows is where this bites hardest. A file with open handles cannot be deleted, and the delete fails immediately rather than waiting. A retry loop alone is nearly enough - the children exit on their own shortly after - but the timing window is wide enough to fail a whole install.
The fix
Terminate the process tree before the wrapper's pipes close, while the launcher still exists for the tree kill to walk, then retry the cleanup:
taskkill /T /F /PID <launcher-pid>
The upstream fix does exactly that, and retries disposable-profile removal up to ten times at 100 ms intervals for the Busy, PermissionDenied and Unknown errors that linger while handles drain.
The general shape matters more than the product. Any installer, test harness or sandbox that spawns children out of a temp directory owns their exit before it owns the delete. Join child exit first, remove second, and never let a cleanup failure overstate itself as a corrupt download.