What is the cause of BI 7.0 Process chain encountered sudden stop on the next metachain?

Hi everyone.

I would like to get your opinion on this issue. I have 10 metachains which loads master data to an openhub. But last week we encountered an issue on one of the metchain. The metachain 0mat_unit did not run but the preceeding metachain 0mat_sales run successfully and did not prompt any error message or any short dump message and its status is green but the next chain the 0mat_unit did not run. I just did manual loading and everythings goes fine. I just want to know what might be the cause of it. We did not do any changes in the metachain so its not possible that the metachain is deactivated. the start variant of 0mat_unit is metachain API so it should run after the 0mat_sales was finished on its job. Any idea on this? thank you very much