I went back to the scanner and gave it another wipe with alcohol and tried again and there were no lines.
That's comforting!
The cyan lines associated with the leaf and in the center of the image do indeed look like typical 'calibration-area' lines, although other causes can also play a role. Especially the fact that they're seemingly pure cyan suggests they're happening on the red channel, only. This means it can also be tiny dust on the sensor strip itself, or a malfunction in the actual sensor. The line just left of the vertical twig and just left of center frame looks like a different kind of problem. It's between the red lines in the snippet below. This could be a hairline scratch on the negative.
When troubleshooting dust in the calibration area of the platen, keep in mind that the dust can also adhere to the
underside of the glass. At some point with these scanners it becomes necessary to clean the glass on both sides. It's not difficult to open up the scanner and lift out the glass, fortunately.