Big matter caused by "delay taking effective" when a rule is updated in branch

E.g. in develop env, I updated a flow in a branch, checked in, then start to test.

Found that, randomly, the old version flow (merged before) is stilled being called instead of updated flow.

After 2 days waiting, the issue "auto resolved", all test cases can refer to updated flow in branch.

Any possible reason? (For info, the flow is a following step after a "Wait" step)