doc: known_issues: add known issue about assertion in Host

Add known issue about assertion in Host that can happen if sysworkq is
blocked and app or host is trying to send sync command from any other
thread.

Signed-off-by: Pavel Vasilyev <[email protected]>

Author: PavelVPV

doc/nrf/releases_and_maturity/known_issues.rst

@@ -435,6 +435,15 @@ NCSDK-30959: The Bluetooth subsystem might deadlock when :kconfig:option:`CONFIG
 
   **Workaround:** Enable the :kconfig:option:`CONFIG_BT_HCI_ACL_FLOW_CONTROL` Kconfig option or do not call the blocking API from any of the Bluetooth Host callbacks.
 
+.. rst-class:: v3-1-1 v3-1-0 v3-0-2 v3-0-1 v3-0-0 v2-9-2 v2-9-1 v2-9-0-nRF54H20-1 v2-9-0 v2-8-0 v2-7-99-cs2 v2-7-99-cs1 v2-7-0
+
+NCSDK-35430: Assertion can happen in the Bluetooth Host if an application is trying to send a synchronous command while the system workqueue is blocked
+  If the Bluetooth Host or an application blocks the system workqueue, the Bluetooth Host TX processor cannot send commands or data towards the Controller.
+  If this happens when a separate thread tries to send a synchronous command, an assertion can occur.
+  This assertion is highly possible if the application is trying to send a synchronous command from the :c:member:`bt_conn_cb.connected` callback.
+
+  **Workaround:** Increase the value of the :kconfig:option:`CONFIG_BT_BUF_CMD_TX_COUNT` Kconfig option.
+
 Bluetooth Mesh
 ==============