Concatenation using mkvmerge fails

[root@test ~]# av1an -c mkvmerge --sc-method fast -i onk01.mkv  --resume
INFO [av1an_core::settings] Input: 1920x1080 @ 23.976 fps, YUV420P10LE, SDR
INFO [av1an_core::settings] encoding resumed with 1084/1084 chunks completed (0 remaining)
Queue 0 Workers 0 Passes 2
Params: --threads=8 --cpu-used=6 --end-usage=q --cq-level=30 --tile-columns=1 --tile-rows=0
ERROR [av1an_core::concat] mkvmerge concatenation failed with output: Output {
    status: ExitStatus(
        unix_wait_status(
            512,
        ),
    ),
    stdout: "mkvmerge v79.0 ('Funeral Pyres') 64-bit\nError: The file '01020.ivf' could not be opened for reading: open file error.\n",
    stderr: "",
}
command: cd ".21084da/encode" && "mkvmerge" "@../options.json"
  00:00:00 ▕█████████████████████████████████████████████████▏ 100%  117921/117921 (825706.75 fps, eta 0s, 731.4 Kbps, est. 428.85 MiB)
Error: mkvmerge concatenation failed
[root@test ~]# ls -l .21084da/encode/01020.ivf
-rw-r--r-- 1 root root 534286 Oct 20 16:31 .21084da/encode/01020.ivf

using av1an 0.4.1-1 on Arch Linux x86_64

Not sure what is happening here. The file exists as you can see.

master-of-zen / Av1an

Concatenation using mkvmerge fails #786