Hi, Michal-

I pinged some MEICA experts here, and the advice was:
That particular error message could apparently come up relatively often in the older (Kundu et al.) MEICA, but the recommended way to solve/address/avoid it would be to use the newer tedana (Du Pre et al.):
https://tedana.readthedocs.io/en/stable/

It integrates into your afni_proc.py command in essentially the exact same way as using the older version, just using a different "-combine_method METHOD", such as m_tedana instead of tedana. Here is the AP help snippet about MEICA group tedana option usage:

---- combine methods that use tedana from the MEICA group ----

       The MEICA group tedana is specified with 'm_tedana*' methods.

          This tedana requires python 3.6+.

          AFNI does not distribute this version of tedana, so it must
          be in the PATH.  For installation details, please see:

             [tedana.readthedocs.io]

        methods
        m_tedana         : tedana from MEICA group (dn_ts_OC.nii.gz)
        m_tedana_OC      : tedana OC from MEICA group (ts_OC.nii.gz)
        m_tedana_m_tedort: tedana from MEICA group (dn_ts_OC.nii.gz)
                           "tedort" from MEICA group
                           (--tedort: "good" projected from "bad")

How does that seem?

Note that the older (Kundu et al.) MEICA approach only works in Python 2.7; the newer (Du Pre et al.) approach only works in Python 3.*. If you are using Conda to manage your Python environments, we actually have some notes about what you would want to include for using the latter in the environment_afni_ted.yml described here:
[afni.nimh.nih.gov]

--pt