Troubleshooter does not work due to RangeError: Invalid array length

[HarHarLinks]

Uncaught (in promise) RangeError: Invalid array length
    at paintFingerprintDiff (<anonymous>:180:19)
    at renderTroubleshooter (<anonymous>:3:5)
    at HTMLSelectElement.episodeChanged (<anonymous>:162:17)

which is

intro-skipper/ConfusedPolarBear.Plugin.IntroSkipper/Configuration/visualizer.js

Line 180 in 686c978

fpDiff.length = Math.min(fp1.length, fp2.length) - Math.abs(offset);

offset is NaN here.
Going one step back to

intro-skipper/ConfusedPolarBear.Plugin.IntroSkipper/Configuration/visualizer.js

Line 3 in 686c978

paintFingerprintDiff(canvas, lhs, rhs, Number(offset.value));

offset is at least sometimes a number, as tested in the console e.g.

1135602

however offset.value is just undefined.