idevicebackup2 unback hangs

[Vaelatern]

After extracting almost the entire backup, the command seems to hang. When running strace, I see regular calls of:

select(4, [3], NULL, NULL, {tv_sec=30, tv_usec=0}) = 1 (in [3], left {tv_sec=29, tv_usec=999999})
read(3, "", 5)                          = 0
select(4, [3], NULL, NULL, {tv_sec=30, tv_usec=0}) = 1 (in [3], left {tv_sec=29, tv_usec=999999})
read(3, "", 5)                          = 0
select(4, [3], NULL, NULL, {tv_sec=30, tv_usec=0}) = 1 (in [3], left {tv_sec=29, tv_usec=999999})
read(3, "", 5)                          = 0
select(4, [3], NULL, NULL, {tv_sec=30, tv_usec=0}) = 1 (in [3], left {tv_sec=29, tv_usec=999999})
read(3, "", 5)                          = 0
select(4, [3], NULL, NULL, {tv_sec=30, tv_usec=0}) = 1 (in [3], left {tv_sec=29, tv_usec=999999})
read(3, "", 5)                          = 0
select(4, [3], NULL, NULL, {tv_sec=30, tv_usec=0}) = 1 (in [3], left {tv_sec=29, tv_usec=999999})

This is right after unpacking a small plist file.

A possible confounding factor: the phone storage is nearly completely full.