I Want to Return My TCL 55C745 TV Due to Random Screen Brightness Fluctuations

When I received the TCL 55C745 55" 139 cm Satellite Receiver 4K Ultra HD Google Smart Gaming QLED TV from Trendyol, the screen brightness began fluctuating—dimming and brightening momentarily—within the first week of use while watching TV. This issue continued at brief intervals. I contacted the Trendyol seller through the Q&A section and was told that the technical service team would handle it. It took a week or two to reach the service and schedule an appointment. When the technician came, I explained the issue and requested a return or replacement of the product. However, they said they couldn’t do that immediately and would first need to inspect it. After checking the settings, they claimed everything was fine. Yet we are still experiencing the problem. They then asked us to record the issue on video. Since we work full-time, it's not possible for us to leave the TV on all day just to capture a video—especially when the issue occurs unpredictably. I’ve never heard of such a policy before. They expect us to drop everything and record the TV all day. I want to return the product. I will also file a complaint with Consumer Rights. They have not offered us a fair solution, and my satisfaction is zero.