Customer wanted a TV cabinet measuring inside 40" x 17". Before I have
gone too far she tells me she mismeasured the TV; it needs to be 40" x 20".

Deliver it; turns out the TV is 20.2" high. Argh.

Well, the bottom piece is butt jointed between the sides, so in principle I
could remove the bottom and put a new bottom below the sides. That would
gain 7/8". It would be less than desired, but at least it would fit.

The bottom is fastened in with pocket screws and Titebond Molding & Trim
glue; I wanted something that wouldn't run while I was putting the bottom
in.
Any way to unglue it? I can remove the screws and saw the bottom off but it
would be better to unglue it if possible.

Yeah, I should have measured it myself, but she is 45 miles away. Yeah,
driving 90 miles would have been better than this.