Timing gets borked on "Render Video…" export.

Actions:
• import a video (one that runs fine in QuickTime and other video apps).

• add some text captions.

• use "Render Video…" to save it as an MP4 file.

Result:
The video with a previous length of X (no matter the length), now runs in half about one-half a second—super crazy fast-forward, instantly finishes.

I feel like I must have somehow, somewhere, accidentally changed setting of something.

Photoshop started doing this about three or four days ago to any and every video I render.

It's a huge problem. Multiple videos effected. I'm absolutely stumped.
Grateful for any help.