@martin.grofcik But I get this error whenever I restart my tomcat. After 2-3 restarts all timer entity error gets cleared and it starts working fine.
For deleting existing model & deployment, I am using the following code.
<java>
    public String deleteModel(String modelName, String processName) {
        RepositoryService repositoryService = ProcessEngines.getDefaultProcessEngine().getRepositoryService();
        RuntimeService runtimeService = ProcessEngines.getDefaultProcessEngine().getRuntimeService();
        HistoryService historyService = ProcessEngines.getDefaultProcessEngine().getHistoryService();
        List<Model> models = repositoryService.createModelQuery().modelName(modelName).list();
        if (models != null && models.isEmpty()) {
            return "Model Not Found";
        }
        for (Model model : models) {
            List<ProcessDefinition> processDefinitions = repositoryService.createProcessDefinitionQuery().
                    processDefinitionKey(processName).list();
            for (ProcessDefinition processDefinition : processDefinitions) {
                try {
                    List<HistoricProcessInstance> historicProcessInstances = historyService.createHistoricProcessInstanceQuery().processDefinitionKey(processName).list();
                    for (HistoricProcessInstance historicProcessInstance : historicProcessInstances) {
                        runtimeService.deleteProcessInstance(historicProcessInstance.getId(), "Model Deleted");
                        historyService.deleteHistoricProcessInstance(historicProcessInstance.getId());
                    }
                } catch (Exception e) {
                    LOGGER.error("Error deleting model", e);
                }
                try {
                    repositoryService.deleteDeployment(processDefinition.getDeploymentId(), true);
                } catch (Exception e) {
                    LOGGER.error("Error deleting model", e);
                }
            }
            try {
                repositoryService.deleteModel(model.getId());
            } catch (Exception e) {
                LOGGER.error("Error deleting model", e);
            }
        }
        return "Deleted Successfully";
    }
</java>
Is there some issue in the above code which is leading to the current exceptions.