Attached is a simple reproducer: zupa.
To reproduce:
1. Open three shells.
2. In shell 1 type: while true; do ./zupa status; done
3. In shell 2 type: while true; do ./zupa start; done
4. In shell 3 type: while true; do ./zupa stop; done

Alternatively, add another shell with while true; do ./zupa status; done

After some time (~ 1 minute) one or all sessions will hang:
root     23232  0.0  0.0 139164  1240 pts/8    S+   17:21   0:00 screen -S zupa -p main -Q title
root     31799  0.0  0.0 168308 24080 ?        Ss   17:20   0:00 SCREEN -S zupa -d -m bash

I think it has something to do with /var/run/screen-4.6.2/S-root/31799.zupa-queryA
unix  2      [ ACC ]     STREAM     LISTENING     433339114 31799/SCREEN         /var/run/screen-4.6.2/S-root/31799.zupa
unix  2      [ ACC ]     STREAM     LISTENING     433384640 23232/screen         /var/run/screen-4.6.2/S-root/31799.zupa-queryA


strace -p 31799
Process 31799 attached
select(1024, [4 5 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23], [], NULL, NULL

/proc/31799/fd:
lrwx------ 1 root root   64 Jul 26 17:23 4 -> socket:[433339114]
lrwx------ 1 root root   64 Jul 26 17:23 7 -> socket:[433339117]



strace -p 23232
Process 23232 attached
accept(4,

/proc/23232/fd:
lrwx------ 1 root root 64 Jul 26 17:23 4 -> socket:[433384640]

Reproduced on Centos7.
Regards.
Jacek Tomaka