The deck boards look fine. The neat band around the edge has developed a wave. It is tempting to pull it flat and add another screw wherever it disagrees.
Identify the board before repairing it
Find the fascia product name, installation date, and photographs from the build. Check whether the material is fascia supplied for that use or a decking board adapted on site. The fastening detail may be different.
Trex's fascia guidance describes spacers and product-specific fasteners. Use the instructions applicable to the installed product, not those for a visually similar board. A wider screw head is not automatically the required fixing.
Separate movement from an uneven backing
Ask the installer to inspect gaps, fastener placement, and the surface behind the fascia. Record whether the wave changes with weather. A bowed rim or trapped debris calls for a different response from a fastening detail that prevents the fascia moving as intended.
Agree the repair boundary
- Which pieces will be removed and can they be reused?
- What will be corrected behind them?
- Which fasteners and spacing detail will be followed?
- Will colour differences between new and weathered pieces remain visible?
Do not promise yourself an invisible colour match from a small sample. Ask to see the replacement against the existing deck in daylight.
The practical next step is to repair the detail before replacing the appearance. Otherwise the new strip may simply be a fresh version of the same experiment. Photograph the corrected work before the fascia conceals it again.
If the problem is a colour patch rather than a wave, start with the separate guide to rug marks on composite decking.