Google Sheets conditional formatting gradient not applied for values >= 1 and < 2

I have a Google sheet where several columns use a gradient (using traffic light colours - from red to yellow to green) to indicate values from min to max.

This works fine for values less than one, and for values of two or greater, but for some reason values between 1 and 2 just show up as white. I can't see any reason why this might be.

Here is the conditional formatting I have applied:

And here is an example of what it looks like when applied to the spreadsheet:

This seems completely nonsensical to me. The settings are very simple, but they just don't seem to work.

NB I have tried removing the midpoint, and have also tried changing from percentage to min/max values, but neither of these helped.