Fire Behaviour Calculator: Scrolling weirdness - columns are visible behind the sticky columns

**Describe the Bug**
Users have pointed out that it's a bit confusing and seems buggy when they see information behind/between the sticky columns when scrolling.

**Expected Behaviour**
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**Actual Behaviour**
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** Steps To Reproduce**
Steps to reproduce the behaviour:
1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

**Screenshots**
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**Desktop (please complete the following information):**
- OS: [e.g. iOS]
- Browser [e.g. chrome, safari]
- Version [e.g. 22]

**Additional context**
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The issue does not identify a file, entry point, browser, or reproducible steps. Start by locating the Fire Behaviour Calculator table and reproducing horizontal scrolling; the work is done when non-sticky columns are no longer visible behind or between the sticky columns.

Written by the indexing model from the issue text.