Delay when send data to peripheral with Core Bluetooth&

I work with a Bluetooth peripheral. When I connect, I subscribe to its characteristics and get a huge amount of data. The data comes without delay. There is no delay when sending data to the device. After 5 minutes of use, there is a delay in sending data to the device for 30 seconds. After 10 minutes of use, there is a delay in sending data to the device for 2 minutes and so on. Tried at the time of sending instantly unsubscribe from the characteristics-did not help. Tried to do everything without the interface-did not help. Who faced such problem? Is there a solution?