Wavy pattern in 480x272 Resistive display

Hi

We have used touchgfx design in our customized STM32F746G project and using same hardware design of STM32F746G discovery board.While running, some wavy pattern is appearing on screen.I have attached the video for your reference .We have used FREE rtos in our project

while trying ST LCD examples the wavy pattern is not there on display.

To solve that issue I reduced the refresh rate 60Hz to 30hz still the wavy pattern appearing on display content

look at the letter N M in video

Please help me in this issue.