BACKGROUND: Transcatheter edge-to-edge mitral valve repair is now available in many countries and has achieved favourable therapeutic outcomes. However, there have been no reported cases of clip opening while locked (COWL) during the acute phase using the MitraClip G4 system (Abbott, Abbott Park, IL, USA). CASE SUMMARY: We present two cases of COWL occurring at different phases: one immediately after clip release and the other 2 days post-procedure. In both cases, the initial treatment involved the use of the XTW system. Subsequently, an additional XT system was deployed for the deterioration of mitral regurgitation caused by COWL, without any complications. DISCUSSION: The MitraClip G4 system offers four size variations, providing a larger grasping area and increased flexibility for accessing complex lesions. Furthermore, the complication rate decreased with increasing operator experience and device generation. However, it has been reported that COWL can occur after the clip is deployed during TEER. Although the mechanism of COWL is unclear, the nature and mobility of the valve leaflets and the product specificity of the MitraClip may be involved.