TC reported train unable to move.TC checked and confirmed TLCB was tripped. TC normalised TLCB and s et EB -ok. TLCB tripped again when train start to move in Au to mode. Unable to normalise. ERS-15 ~~~~~ L3 3619 & 3620 checked and confirmed TLCB tripped upon propeling. Function checked all CB - ok. Checked PCOS & MDR2 contactor function check - OK. Checked brake system control and MS circuitry wiring - ok. Further checked found car 2620 motoring line wire 36 shorted to ground. OPS20 raised to rectify shorted cables, and to preventively replace TLSK contactor.  Chan GF. 17/08/2020. L3 3619 TLSK replaced. RSW rectified shorted wire no. 36. Function test on both DT cars - OK. M/L test - Passed. Side finding: Wheel flat found on 3620 A1 (20mm x 30mm). M/O raised to AMMC to follow-up.  Goh AT/Selvan. 18/08/2020. Note: Car 2620 motoring line wire 36 was found to be shorted, hence introducing a surge in current which tripped the TLCB. The shorting was caused by torn wire insulation caused by wire abrasion within the coupler connector inner casing. Poor wire routing and missing anti-chafing sleeve from the train manufacturer was identified as the root cause. SMRT will be carrying out interim measures to insulate wires within the coupler casing while reviewing the design with LTA and KHI to add protective sleeve in the coupler casing.