panic: ptrace status unexpected: got 31, wanted stopped

goroutine 593515 [running]:
DIAGNOSIS:
I0501 11:26:06.501573   10748 x:0] ***************************
I0501 11:26:06.501624   10748 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]
I0501 11:26:06.501639   10748 x:0] Version release-20190304.1-163-g8bfb83d0acde
I0501 11:26:06.501644   10748 x:0] PID: 10748
I0501 11:26:06.501650   10748 x:0] UID: 0, GID: 0
I0501 11:26:06.501653   10748 x:0] Configuration:
I0501 11:26:06.501656   10748 x:0] 		RootDir: /syzkaller/managers/main/workdir/gvisor_root
I0501 11:26:06.501659   10748 x:0] 		Platform: ptrace
I0501 11:26:06.501670   10748 x:0] 		FileAccess: shared, overlay: false
I0501 11:26:06.501676   10748 x:0] 		Network: none, logging: false
I0501 11:26:06.501685   10748 x:0] 		Strace: false, max size: 1024, syscalls: []
I0501 11:26:06.501689   10748 x:0] ***************************
D0501 11:26:06.502742   10748 x:0] Load container "/syzkaller/managers/main/workdir/gvisor_root" "ci-gvisor-main-3"
D0501 11:26:06.504367   10748 x:0] Signal container "ci-gvisor-main-3": signal 0
D0501 11:26:06.504386   10748 x:0] Signal sandbox "ci-gvisor-main-3"
D0501 11:26:06.504391   10748 x:0] Connecting to sandbox "ci-gvisor-main-3"
D0501 11:26:06.505934   10748 x:0] urpc: successfully marshalled 96 bytes.
I0501 11:26:06.810894   10748 x:0] Found sandbox "ci-gvisor-main-3", PID: 56590
I0501 11:26:06.810909   10748 x:0] Retrieving sandbox stacks
D0501 11:26:06.811593   10748 x:0] Stacks sandbox "ci-gvisor-main-3"
D0501 11:26:06.811602   10748 x:0] Connecting to sandbox "ci-gvisor-main-3"
D0501 11:26:06.811658   10748 x:0] urpc: successfully marshalled 36 bytes.
W0501 11:26:06.868485   10748 x:0] FATAL ERROR: retrieving stacks: getting sandbox "ci-gvisor-main-3" stacks: urpc method "debug.Stacks" failed: connection reset by peer
retrieving stacks: getting sandbox "ci-gvisor-main-3" stacks: urpc method "debug.Stacks" failed: connection reset by peer