Problem using NRF24L01+ and delays

Hi!
I’m trying to send some data with the NRF24L01+, the RF24 library and two Arduinos (uno).
Everything’s working fine, but when I try to put a delay to the sender (to send data every n milliseconds), thinks don’t work as expected!

If the sender sends data every 10 milliseconds or less → no problem

Serial output:
...
Sending...Yeah!
Sending...Yeah!
Sending...Yeah!
Sending...Yeah!
Sending...Yeah!
...

If the sender sends data every 100, 200, 300,… milliseconds → some error, and when error occurs, the arduino stucks in the write function for about 800 ms

Serial output:
...
Sending...Yeah!
Sending...Error :(
Sending...Yeah!
Sending...Error :(
Sending...Yeah!
Sending...Error :(
...

If the sender sends data every 1000,… milliseconds → some error, and when error occurs, the arduino stucks in the write function for about 800 ms

When I try to send every second or more, the write function returns always false (error).

Any help appreciated! Thanks!!!

The code of the sender:

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
const uint64_t pipe = 0xABCDABCD72LL;
RF24 radio(9, 10); 
int data[2];
static unsigned long previousTime;

//if this value is high, then the write function returns false!!!
unsigned long interv = 10;

void setup() {
  Serial.begin(57600);
  radio.begin();
  radio.openWritingPipe(pipe);
  previousTime = millis() - interv;
}

void loop() {
  //enter the if statement every interv milliseconds
  if (millis() - previousTime > interv) {
    previousTime = millis();
    
    data[0] = 10; //some data
    data[1] = 44;
    
    bool ok = radio.write(data, sizeof(data));
    Serial.print("Sending...");
    if(ok) {
      Serial.println("Yeah!");
    } else {
      Serial.println("Error :(");
    }
  }
}

ps: I already soldered two 10uF capacitors to the NRF24L01+s