ESP32-C3 bleprph example light sleeping rotating current draw

[Camacazi]

I've been experimenting with bringing down the power consumption of BLE advertising on the ESP platform (in particular the ESP32C3 in this case).

Using the bleprph example and setting the RTC clock source to external 32kHz, enabling power management, tickless idle, and modem sleeping on the external crystal (hope I'm not forgetting anything), and enabling light sleeping via the esp_pm component and increasing advertising interval to 2 seconds with transmission power of 3dBm significantly lowers my power consumption to about 0.2mA sleeping and 2.5mA peak advertising.

It's that peak advertising part that's interesting. I notice that it will start off pulling that amount during advertising every 2 seconds, but then each subsequent advertisement it slowly decreases after 20-30 advertisements to a draw of 0.3mA, and then just as slowly as it went down go back up to that peak after a similar time frame. The peak draw pattern is almost sinusoidal.

I'm wondering what would cause the advertising power draw to rotate like this? Anyone seen anything similar?