Meaning of failures reported by stress-ng-pty?

I received the following failure messages from stress-ng-pty:

stress-ng: 19:27:57.21 fail: [3323] stress-ng-pty: ioctl TCSETAF on slave pty failed, errno=4 (Interrupted system call)
 2019-08-07 19:27:57.239
stress-ng: 19:27:57.21 fail: [3322] stress-ng-pty: ioctl TCSETSW on slave pty failed, errno=4 (Interrupted system call)

I believe system calls may in principle be interrupted at any time; is this really a failure?

Using stress-ng-0.10