panic: ptrace status unexpected: got 31, wanted stopped

goroutine 6481711 [running]:
DIAGNOSIS:
I0413 03:23:47.402657   63674 x:0] ***************************
I0413 03:23:47.402711   63674 x:0] Args: [/syzkaller/managers/main/current/image -root /syzkaller/managers/main/workdir/gvisor_root -watchdog-action=panic -network=none -debug -platform=ptrace -file-access=shared -network=none debug -stacks ci-gvisor-main-3]
I0413 03:23:47.402725   63674 x:0] Version release-20190304.1-116-g546a1df7d15f
I0413 03:23:47.402730   63674 x:0] PID: 63674
I0413 03:23:47.402736   63674 x:0] UID: 0, GID: 0
I0413 03:23:47.402746   63674 x:0] Configuration:
I0413 03:23:47.402750   63674 x:0] 		RootDir: /syzkaller/managers/main/workdir/gvisor_root
I0413 03:23:47.402753   63674 x:0] 		Platform: ptrace
I0413 03:23:47.402782   63674 x:0] 		FileAccess: shared, overlay: false
I0413 03:23:47.402809   63674 x:0] 		Network: none, logging: false
I0413 03:23:47.402816   63674 x:0] 		Strace: false, max size: 1024, syscalls: []
I0413 03:23:47.402821   63674 x:0] ***************************
D0413 03:23:47.402853   63674 x:0] Load container "/syzkaller/managers/main/workdir/gvisor_root" "ci-gvisor-main-3"
D0413 03:23:47.411138   63674 x:0] Signal container "ci-gvisor-main-3": signal 0
D0413 03:23:47.411182   63674 x:0] Signal sandbox "ci-gvisor-main-3"
D0413 03:23:47.411189   63674 x:0] Connecting to sandbox "ci-gvisor-main-3"
D0413 03:23:47.411379   63674 x:0] urpc: successfully marshalled 96 bytes.
I0413 03:23:47.995886   63674 x:0] Found sandbox "ci-gvisor-main-3", PID: 62763
I0413 03:23:47.995908   63674 x:0] Retrieving sandbox stacks
D0413 03:23:47.995914   63674 x:0] Stacks sandbox "ci-gvisor-main-3"
D0413 03:23:47.995928   63674 x:0] Connecting to sandbox "ci-gvisor-main-3"
W0413 03:23:47.995990   63674 x:0] FATAL ERROR: retrieving stacks: connecting to control server at PID 62763: connection refused
retrieving stacks: connecting to control server at PID 62763: connection refused