Train undershoot 0.5 meter in AM. TC unable to ATPM to HW due to MCH jammed. TC toggled MS and force d the MCH to ATPM to HW. ~~~~~ 3543 (S) Train undershoot 0.5 meter in AM. TC unable to ATPM to HW due to MCH jammed. TC toggled MS and forced the MCH to ATPM to HW. BDL SB"  Checked 3543 MCH found intermittent jammed. Checked no object obstruction. Checked for undershoot on 3543 - Done. Download ER - No abnormalities in braking. Checked brake status - OK. Brake able to release at coast. No residual pressure in coast mode. Checked all car dump v/v - OK. Able to activate brake unit - OK. No air leak. Break shoe - OK. Redzwan/Chan SW/Aliff/Daniel 45400 For Further Checks.  3543 Found MS has free play when in ATPM mode which can cause MCH to jam. Realigned MS bearing mounting holder bolts. Tested MS movement ok and MCH movement ok. Inspected other bolts to check for looseness ok.  Alan/Anand 45400