multiInstance subprocess of revoking tasks has bug

**Describe the bug**
In the multiInstance subprocess of departments,
if Receiver sends A and then withdraws, Receiver sends B and then withdraws, Receiver sends A and A sends B。
error : No outging sequence flow of element 'Activity_1xk5x7b' could be selected for continuing the process， How to solve it?

**Code**
taskService.complete(taskBo.getTaskId(), processVariables);

**Additional context**
Flowable 6.8.1

Start by reproducing the multi-instance subprocess sequence shown in the issue on Flowable 6.8.1, using taskService.complete(taskBo.getTaskId(), processVariables). Trace the failure around the reported missing outgoing sequence flow from Activity_1xk5x7b. Done means the A/B revoke sequence completes correctly and a regression test covers it.

Written by the indexing model from the issue text.