hAP ac^2 Problems---Extremely Poor Performance found in 2.4G and 5G WiFi

Today, I found that there is a new test candidate available for evaluation. I update the firmware in my hAP ac^2 and the following results as shown in Figures 1 and 2.

It seems that there is not much speed improvement since v6.42r52. The 5G transmission rate, as shown in Figure 2, looks very terrible as it goes up and down. The average speed is around 120Mbps, which is much below any other’s brand ac products. Our user expectation, it keeps at a steady rate of 500Mbps. I am wondering whether the MikroTik Engineering Team is aware of these problems?

Figure 1: 2.4G WiFi Performance

Figure 2: 5G WiFi Performance