panic: ptrace status unexpected: got 31, wanted stopped

goroutine 4074089 [running]:
DIAGNOSIS:
I0520 12:58:07.753542   25672 x:0] ***************************
I0520 12:58:07.753635   25672 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-1]
I0520 12:58:07.753656   25672 x:0] Version release-20190304.1-210-g4a842836e560
I0520 12:58:07.753662   25672 x:0] PID: 25672
I0520 12:58:07.753668   25672 x:0] UID: 0, GID: 0
I0520 12:58:07.753675   25672 x:0] Configuration:
I0520 12:58:07.753678   25672 x:0] 		RootDir: /syzkaller/managers/main/workdir/gvisor_root
I0520 12:58:07.753681   25672 x:0] 		Platform: ptrace
I0520 12:58:07.754170   25672 x:0] 		FileAccess: shared, overlay: false
I0520 12:58:07.754179   25672 x:0] 		Network: none, logging: false
I0520 12:58:07.754184   25672 x:0] 		Strace: false, max size: 1024, syscalls: []
I0520 12:58:07.754189   25672 x:0] ***************************
D0520 12:58:07.755112   25672 x:0] Load container "/syzkaller/managers/main/workdir/gvisor_root" "ci-gvisor-main-1"
D0520 12:58:07.768150   25672 x:0] Signal container "ci-gvisor-main-1": signal 0
D0520 12:58:07.768303   25672 x:0] Signal sandbox "ci-gvisor-main-1"
D0520 12:58:07.776004   25672 x:0] Connecting to sandbox "ci-gvisor-main-1"
D0520 12:58:07.780120   25672 x:0] urpc: successfully marshalled 96 bytes.
I0520 12:58:08.354273   25672 x:0] Found sandbox "ci-gvisor-main-1", PID: 61359
I0520 12:58:08.354286   25672 x:0] Retrieving sandbox stacks
D0520 12:58:08.354484   25672 x:0] Stacks sandbox "ci-gvisor-main-1"
D0520 12:58:08.354493   25672 x:0] Connecting to sandbox "ci-gvisor-main-1"
D0520 12:58:08.354555   25672 x:0] urpc: successfully marshalled 36 bytes.
W0520 12:58:08.449869   25672 x:0] FATAL ERROR: retrieving stacks: getting sandbox "ci-gvisor-main-1" stacks: urpc method "debug.Stacks" failed: connection reset by peer
retrieving stacks: getting sandbox "ci-gvisor-main-1" stacks: urpc method "debug.Stacks" failed: connection reset by peer