The maker of a shinkansen undercarriage on which severe cracks were found last year has apologized over the incident that could have caused a derailment, saying there was vulnerability in its quality management system.

S The maker [of] a shinkansen undercarriage 新幹線の装置のメーカー
どんな→
[on] [which]
S severe cracks 隙間が
V [were found] (last year) 見つかった

V [has apologized] 謝罪しました
補足
[over] the incident 事件
どんな→
[that]
V [could have caused]
O a derailment 脱線
,

補足
V [saying]
O (that)

S there
V [was]
O vulnerability 脆弱
どんな→
[in] its quality management system. 管理システム