Serial + BLE + I2C + Timer + GPIO -> serial not works

We are developing an application on the nRF52840 kit with SDK 15.2. We are using Keil as compiler. I have started developmet my application with the example ble_app_cscs. In this example I added the libraries for use the serial, I2C, timer and GPIO.
After that, when I start the application and I connecting the nRF52840 device with app and I receiveng data from UART, after a random time the serial stops to work, while the I2C, GPIO and timer works correctly.
The firmare is running and it communicate with the App but the function that receive from the Uart return always no data. The data continue to come from Uart, I can see them with oscylloscope, but the receive function say always no data. This happen after a random time, it can be immediatly or after some minutes.
When te uart stops to receive data, the error that it return is the numer 13 : timeout.
If I use the BLE or the UART separatly they work fine. I attached all project.
Do you have any idea about this problem?

ble_app_cscs.zip