Train undershoot platform by 1 metres inAuto mode. Proceeded in ATPM mode to the headwall. ~~~~~ Train undershoot platform by 1 metres in    Checked brake pressure status ok. Physically check and found 2501-B3 brake shoe unable to release at coast. All other brakes ok. OP20 raised to replace service brake unit. N.ASANKAR/18.04.21 --------------------- To replace 2501 B3 service brake unit and carryout function check.    Replaced 2501 B3 service brake unit. Function test ok. N.AKUMAR/19.04.21 ---------------------