The issue that was reported in 2024 is occurring again as of Aug 4, 2026 - the PDF export did not behave this way on July 30, 2026.
Solved: Tables in PDF exports have 3D effect
[CONFCLOUD-80335] Tables in PDF Export Display Shadows and Extra Lines - Create and track feature requests for Atlassian products.
Please reapply the previous fix that resolved this.
Thank you