The answer to 'why is my flashing curling shingles' is that the flashing is likely not properly installed or sealed, causing it to pull away from the roof and curl the surrounding shingles. This can happen due to poor initial installation, age and weathering, or improper repairs. Curling flashing can allow water to seep under the shingles, leading to leaks and damage.
To fix curling flashing, you'll need to inspect the area and re-secure or replace the flashing as needed. This may require removing and re-installing shingles. If the damage is extensive or the flashing is difficult to access, it's best to call in a professional roofer to ensure the problem is properly addressed.