optimistic_trx causes a query to hang

13:32:14   info   : (1) (My-Service); > Autocommit: [disabled], trx is [not open], cmd: (0x3) COM_QUERY, plen: 21, type: sql::TYPE_SESSION_WRITE|sql::TYPE_BEGIN_TRX|sql::TYPE_DISABLE_AUTOCOMMIT, stmt: SET autocommit=0

13:32:14   info   : (1) [readwritesplit] (My-Service); Session write, routing to all servers.

13:32:14   info   : (1) [readwritesplit] (My-Service); Route query to replica: server1

13:32:14   info   : (1) [readwritesplit] (My-Service); Route query to replica: server2

13:32:14   info   : (1) [readwritesplit] (My-Service); Route query to primary: server3

13:32:14   info   : (1) [readwritesplit] (My-Service); Will return response from 'server3' to the client

13:32:14   info   : (1) [readwritesplit] (My-Service); Reply complete from 'server2' (OK: 0 warnings)

13:32:14   info   : (1) [MariaDBProtocol] (My-Service); Added COM_QUERY to history with ID 4: SET autocommit=0 (result: OK)

13:32:14   info   : (1) [readwritesplit] (My-Service); Reply complete from 'server1', discarding it: OK: 0 warnings

13:32:14   info   : (1) [readwritesplit] (My-Service); Reply complete from 'server3' (OK: 0 warnings)

13:32:14   info   : (1) (My-Service); > Autocommit: [disabled], trx is [open], cmd: (0x3) COM_QUERY, plen: 10, type: sql::TYPE_BEGIN_TRX, stmt: BEGIN

13:32:14   info   : (1) [readwritesplit] (My-Service); Storing query (len: 10 cmd: 3), expecting -1 replies to current command: BEGIN. Would route TARGET_SLAVE to 'server1'.

13:32:15   info   : (1) [readwritesplit] (My-Service); New COM_QUERY received while query execution is active:  SELECT 1

13:32:46   info   : (1) [MariaDBProtocol] Client disconnected without sending a COM_QUIT.

13:32:46   info   : (1) Stopped My-Service client session [1]