I can't reproduce the issue anymore in the following versions. The feature works quite nicely.

texmacs 2.1.1

guix describe
Generation 52	Dec 23 2021 11:56:54	(current)
  guix 037c2b6
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 037c2b6d3acdf7f5b68ecb3024ef90bce85922df



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Luis Felipe López Acevedo