Sorry for the slow reply, fireworker. Work got in the way. First, thanks for the additional tips and thoughts.

Before running DISKPART to change the partition size, I decided to check for for bad sectors. The only Toshiba HD diagnostic tool I could find for my model (Satellite A660) wouldn't run in the WinRE Command window ("... not compatible with the version of Windows you're running ..."), so I ran chkdsk c: /b and got the report shown in the screenshot below.
IMG_0938r75.jpg

Since Stage 1 (scrolled off the top) reported "0 bad files processed ...", the only suspicious results were from Stage 5 ("Correcting errors in the volume bitmap.") and the final line ("Failed to transfer logged messages ..."). Unfortunately, whatever bitmap errors were corrected didn't solve my problem.

Guess that leaves running DISKPART as you suggested, increasing the size of partition #1 by 1 GB so it matches the size of that partition in the BR 14 backup (452 GB). After watching your YouTube video and reading the Help for DISKPART, it appears this is the correct sequence of commands:
DISKPART> select disk=0
DISKPART> select partition=2
DISKPART> extend size=1024

Does that look right?