panic: ptrace status unexpected: got 31, wanted stopped

goroutine 3050 [running]:
DIAGNOSIS:
I0502 21:54:10.534674   47839 x:0] ***************************
I0502 21:54:10.534740   47839 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-2]
I0502 21:54:10.534752   47839 x:0] Version release-20190304.1-163-g8bfb83d0acde
I0502 21:54:10.534757   47839 x:0] PID: 47839
I0502 21:54:10.534762   47839 x:0] UID: 0, GID: 0
I0502 21:54:10.534765   47839 x:0] Configuration:
I0502 21:54:10.534768   47839 x:0] 		RootDir: /syzkaller/managers/main/workdir/gvisor_root
I0502 21:54:10.534771   47839 x:0] 		Platform: ptrace
I0502 21:54:10.534779   47839 x:0] 		FileAccess: shared, overlay: false
I0502 21:54:10.534790   47839 x:0] 		Network: none, logging: false
I0502 21:54:10.534795   47839 x:0] 		Strace: false, max size: 1024, syscalls: []
I0502 21:54:10.534805   47839 x:0] ***************************
D0502 21:54:10.534834   47839 x:0] Load container "/syzkaller/managers/main/workdir/gvisor_root" "ci-gvisor-main-2"
D0502 21:54:10.536376   47839 x:0] Signal container "ci-gvisor-main-2": signal 0
D0502 21:54:10.536394   47839 x:0] Signal sandbox "ci-gvisor-main-2"
D0502 21:54:10.536404   47839 x:0] Connecting to sandbox "ci-gvisor-main-2"
D0502 21:54:10.536585   47839 x:0] urpc: successfully marshalled 96 bytes.
I0502 21:54:10.782945   47839 x:0] Found sandbox "ci-gvisor-main-2", PID: 43066
I0502 21:54:10.782963   47839 x:0] Retrieving sandbox stacks
D0502 21:54:10.782969   47839 x:0] Stacks sandbox "ci-gvisor-main-2"
D0502 21:54:10.782974   47839 x:0] Connecting to sandbox "ci-gvisor-main-2"
D0502 21:54:10.783041   47839 x:0] urpc: successfully marshalled 36 bytes.
W0502 21:54:10.846499   47839 x:0] FATAL ERROR: retrieving stacks: getting sandbox "ci-gvisor-main-2" stacks: urpc method "debug.Stacks" failed: connection reset by peer
retrieving stacks: getting sandbox "ci-gvisor-main-2" stacks: urpc method "debug.Stacks" failed: connection reset by peer