That "catastrophic failure" message (usually Error 0x80004005 on Windows) is incredibly frustrating, but your hunch is spot on.

Yes, the lack of storage is almost certainly the root cause. When an iPhone completely runs out of space while recording, a few things happen behind the scenes that cause this error:

1. Unfinalized File: The video file likely didn't get to "close" properly when the storage hit zero, leaving the file header corrupted or incomplete.
2. Zero Cache Space: Windows relies on the iPhone's filesystem to handle the transfer protocol (MTP). Without a few megabytes of free space on the phone to create temporary cache or index files for the transfer, the connection just collapses, resulting in that dramatic "catastrophic failure" error.
3. Locked State: Because the phone's iOS is struggling to index the broken file, it locks it, which is why your PC can't delete it either.

Here is how you can break the deadlock and get that video off (or at least free up your phone).

Step 1: Breathe Life Back into the iPhone's Storage

Before trying to move the giant video again, you must give the phone's operating system some room to breathe.

• Go to Settings > General > iPhone Storage.
• Delete a few unused apps, clear some large Safari caches, or delete some old, unimportant photos or videos that you know are safely backed up.
• Aim to free up at least 1 GB to 2 GB of space.
• Crucial: Once you've freed up the space, restart your iPhone. This forces iOS to rebuild its file index and recognize the newly available cache space.

Step 2: Try Copying Again (With a Robust Method)

Standard Windows File Explorer is notorious for choking on large or unfinalized iPhone video files. Try these alternatives instead:

Method A: Use the Windows "Photos" App (Instead of File Explorer)

Instead of dragging and dropping from the DCIM folder in File Explorer:

1. Open the native Photos app in Windows.
2. Click Import (top right) > From a connected device.
3. Let it scan, select just that one video, and try importing it. The Photos app handles the iOS transfer protocol slightly better than raw File Explorer.

Method B: The Cloud Bypass (If the file isn't massive)

If the video isn't dozens of gigabytes long, see if the phone can upload it directly rather than sending it over a cable.

• Open the Files app on your iPhone.
• Go to your Photos, select the video, tap the Share icon, and choose Save to Files.
• From there, upload it to Google Drive, OneDrive, or iCloud Drive. Once it's in the cloud, you can download it safely to your PC.

Method C: Use a Third-Party Transfer Tool

If Windows File Explorer keeps crashing, free tools like 3uTools or iFunBox bypass standard Windows MTP limitations and read the raw storage of the iPhone directly. They are often able to pluck out "corrupted" or unfinalized .mp4/.mov files that Windows throws a fit over.

Step 3: Deleting the File

If you just want to get rid of it and your PC won't let you:

1. Disconnect the iPhone from the PC entirely.
2. Try deleting it directly on the iPhone via the Photos app.
3. If it refuses to delete or keeps reappearing, go to Settings > General > iPhone Storage, scroll down to Photos, and see if you can manage and delete large videos from that menu instead.
4. Don't forget to empty the Recently Deleted folder in the Photos app to actually reclaim the space!