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.

@zmrzli Make sure you are sending the correct length and AD types according to the ADVERTISING AND SCAN RESPONSE DATA FORMAT (page 2081 on the Bluetooth 4.2 Core Spec - you can access the specification here https://www.bluetooth.com/specifications/adopted-specifications ). If you're looking to use BLE advertising packets to send your data you probably want to use AD type 0xFF (Manufacturer Specific Data) followed by the 2 company identifier octets. So your format should be 1 byte length + 0xFF + <2 bytes company identifier> + your data then filled with 00 until the 31 byte limit. You can't read improperly formatted advertising data.