My mariadb columnstore cluster has 2 UM's and 4 PM's either one um is down then not able access the database

My mariadb columnstore cluster has 2 UM's and 4 PM's either one um is down the system goes into busy init state and come backs to active state but data base is not accessible the below error shows ERROR 1815 (HY000): Internal error: Lost connection to ExeMgr. Please contact your administrator. after restarting the columnstore cluster it works .