I have made the test with scan intervals and scan windows equal to 10 ms. static esp_ble_scan_params_t ble_scan_params = { .scan_type = BLE_SCAN_TYPE_ACTIVE, .own_addr_type = BLE_ADDR_TYPE_PUBLIC, .scan_filter_policy = BLE_SCAN_FILTER_ALLOW_ALL, .scan_interval = 0x10, .scan_window = 0x10 }; The results are better but still not as good as v1.20.3.b0 Beta Firmware was. With the new values, I raised up to 60% of advertisement frames catched. Always with the same conditions and 500 ms as advertisement interval.

I never managed to reproduce the Core Dump but I found this : https://github.com/pycom/pycom-micropython-sigfox/commit/3f690a5733d31ff938aad6219c498f7d1bf98346 A bug fix, the issue was not resolved in the version I used. This issue could explain the core dump I encountered. The issue is fixed in the last beta version (v1.20.3.b3) and in the last release (1.20.2.r4) of the firmware.