TimerTask stops after a while

Question

I set a timer to do some commands in SQL after a 1-hour interval, but it runs a few times 4-5 and then stops running, although other timers set at higher intervals continue to work. What would be the problem? I have absolutely no error in nohup.

public static void timer025() {
    TimerTask t025 = new TimerTask() {

        @Override
        public void run() {
            for (Client c : Load.api.getClients()) {
                if (c.isRegularClient() && Load.PlayerExist(c.getUniqueIdentifier())) {
                    Load.api.sendPrivateMessage(c.getId(),
                            "[b]123[/b]");
                    mysql.update("UPDATE game SET coins = coins+0.25 WHERE game.clientid = '"
                            + c.getUniqueIdentifier() + "'");

                }
            }
        }
    };

    TimerTask t026 = new TimerTask() {

        @Override
        public void run() {
            for (Client c : Load.api.getClients()) {
                if (c.isRegularClient() && Load.PlayerExist(c.getUniqueIdentifier())) {
                    if (c.getChannelId() == 1238292) {
                        Load.api.sendPrivateMessage(c.getId(),
                                "[b]1234");
                        mysql.update("UPDATE game SET coins = coins+300 WHERE game.clientid = '"
                                + c.getUniqueIdentifier() + "'");
                    } else {
                        Load.api.sendPrivateMessage(c.getId(),
                                "[b]12345[/b]");
                        mysql.update("UPDATE game SET coins = coins+150 WHERE game.clientid = '"
                                + c.getUniqueIdentifier() + "'");

                    }
                }
            }
            int client = api.getServerInfo().getClientsOnline();
            int ret = 200 * client;
            mysql.update("UPDATE wallet SET coins = coins-" + ret + " WHERE wallet.uswall = 'mainwall'");
        }
    };



    Timer t = new Timer();
    t.schedule(t025, 1000 * 60 * 15, 1000 * 60 * 15);
    t.schedule(t026, 1000 * 60 * 60, 1000 * 60 * 60);
}