When using COC server and send is stalled, disconnects are not detected

We have an NRF5340 device running Nimble Peripheral. It has a COC server and a GATT server. We connect from a PC application and the device starts streaming data to the PC. Sometimes we get a stalled, then unstalled and everything continues. But sometimes we get a stalled and the PC side gets a disconnect (Connection time-out). The Nimble side doesn't give a GAP disconnect event and just nothing. It never detects the disconnect. We tried manually disconnecting (using both *ble_l2cap_disconnect* and *ble_gap_terminate* (both return 0), but nothing happens. Maybe some bottom layer/queue is still locked?