When I restart a worker whose number is 10, his number will change. An error message appears

[btcioner]

Describe the bug
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To Reproduce
Steps to reproduce the behavior:

1. Run '...'
2. See error

2020-08-25T15:56:18.104Z	WARN	advmgr	sector-storage/sched_watch.go:89	worker 10 dropped
2020-08-25T15:56:18.104Z	DEBUG	advmgr	sector-storage/sched.go:515	task done	{"workerid": 10}
2020-08-25T15:56:18.104Z	WARN	sectors	storage-sealing/fsm.go:403	sector 15 got error event sealing.SectorSealPreCommit2Failed: seal pre commit(2) failed: handler: websocket connection closed
2020-08-25T15:56:18.104Z	WARN	sectors	storage-sealing/fsm.go:403	sector 27 got error event sealing.SectorSealPreCommit2Failed: seal pre commit(2) failed: handler: websocket connection closed
2020-08-25T15:56:18.105Z	INFO	sectors	storage-sealing/states_failed.go:19	SealPreCommit2Failed(15), waiting 59.89472877s before retrying
2020-08-25T15:56:18.105Z	INFO	sectors	storage-sealing/states_failed.go:19	SealPreCommit2Failed(27), waiting 59.894235371s before retrying
2020-08-25T15:56:19.104Z	ERROR	advmgr	sector-storage/sched.go:672	timeout closing worker manager goroutine 10

Repeat.....

2020-08-26t01:40:01.100z error advmgr section storage/ sched.go:318	 worker referenced by windowRequest not found (worker: 10)
2020-08-26T01:40:01.100Z	ERROR	advmgr	sector-storage/ sched.go:318	 worker referenced by windowRequest not found (worker: 10).
2020-08-26T02:29:59.252Z	ERROR	advmgr	sector-storage/sched.go:318	worker referenced by windowRequest not found (worker: 10)
2020-08-26T02:29:59.252Z	ERROR	advmgr	sector-storage/sched.go:318	worker referenced by windowRequest not found (worker: 10)
2020-08-26T02:29:59.252Z	ERROR	advmgr	sector-storage/sched.go:318	worker referenced by windowRequest not found (worker: 10)
2020-08-26T02:29:59.252Z	ERROR	advmgr	sector-storage/sched.go:318	worker referenced by windowRequest not found (worker: 10)
2020-08-26T02:29:59.252Z	ERROR	advmgr	sector-storage/sched.go:318	worker referenced by windowRequest not found (worker: 10)
2020-08-26T02:29:59.252Z	ERROR	advmgr	sector-storage/sched.go:318	worker referenced by windowRequest not found (worker: 10)
2020-08-26T02:29:59.252Z	ERROR	advmgr	sector-storage/sched.go:318	worker referenced by windowRequest not found (worker: 10)

Expected behavior
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Version (run lotus version):
v0.5.2
Additional context
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[flyworker]

same issue found on v 0.5.6