This situation is mostly a problem of the switching power supply, which belongs to the secondary current overload self-protection, that is to say, the secondary current overload of the power supply is greater than the conventional one. What you said should be mostly a problem of the line output tube, which should be a soft breakdown. The possibility of the video output stage is not high, so we should focus on checking the line level. In other places, the probability of damage is low because of the small voltage and low current. In addition, this problem will also occur if the performance of the output tube of the power supply itself is degraded or there is soft breakdown.