The solution is found:

esp_log_level_set("wifi", ESP_LOG_WARN);

P.S.
printing messages warning and error level only

After the last update SDK, there was a problem. On stdout messages are issued:
.......
I (833688) wifi: send null to keep active
I (843688) wifi: send null to keep active
I (853688) wifi: active cnt: 2
I (863688) wifi: send null to keep active
I (873688) wifi: send null to keep active
I (883688 ...

Miracles with RMT: the interface earned without any significant changes !
Than to explain it I do not know - "impure force".
The control function is as follows (сopy of the function from https://github.com/FozzTexx/ws2812-demo):
void ws2812_setColors(unsigned int length, rgbVal *array)
{
wlen ...

Could you give us some more details re what broke (Tx/Rx/both/...)? It would be really awesome if you also could make a Github issue for this ( here ), that makes it easier for us to track it and inform you when we fix it.

I think the transmission (tx) has broken because it is used to control the ...

Good day.
In my project (mqtt_client + ws2812) i used SDK from https://github.com/espressif/esp-idf and example from https://github.com/FozzTexx/ws2812-demo for control ws2812. To control leds in this example use the RMT interface.
This example worked well until I updated SDK (last update 5 days ago ...