Smartsolar firmware 1.74 causing slow ramp down of harvested power

[puchong]

After updating the firmware, the 70/15 MPPT goes from the max harvested 85W, slowly down by 1W or 2W every second, until it reaches 9W and battery voltage roughly 11.6V. By then I have the load terminals on the MPPT shut off, which also disconnect the Soyosource grid tie inverter through a power transistor. After load disconnected, the MPPT can charge the battery at 85W again, and the cycle continues (see screenshot). Is this an expected behaviour? This was not how it works with the previous firmware 1.68.