Failing addon releasebranch_7_8 (Python 3.6) pipeline

Hi devs,

I regularly receive

releasebranch_7_8 (Python 3.6)
Process completed with exit code 1.

(e.g., https://github.com/OSGeo/grass-addons/actions/runs/675694073)

which is a bit confusing for me since we (I believe) already fixed the issues:

Executing <python3 -m grass.gunittest.main --grassdata /home/runner
--location nc_spm_full_v2alpha2 --location-type nc --min-success 60>
...
generate_manpage_images from ./vector/v.stream.order failed
test_stream_order from ./vector/v.stream.order failed (2 tests failed)
test_pygbif_import from ./vector/v.in.pygbif failed (3 tests failed)
test_v_db_pyupdate from ./vector/v.db.pyupdate failed (2 tests failed)
r3_forestfrag_trivial from ./raster3d/r3.forestfrag failed (1 test failed)
test_whatcsv from ./temporal/t.rast.whatcsv failed (1 test failed)
test_whataggr from ./temporal/t.rast.what.aggr failed (6 tests failed)
test_gpot from ./raster/r.green/r.green.gshp/libgshp failed
test_numbers from ./raster/r.sample.category failed
r_extract_test from ./raster/r.extract failed (2 tests failed)
r_object_geometry_test from ./raster/r.object.geometry failed (2 tests failed)
test_base_resolution from ./raster/r.in.pdal failed
r_forestfrag_trivial from ./raster/r.forestfrag failed (1 test failed)
r_forestfrag_xy from ./raster/r.forestfrag failed (1 test failed)
test_append from ./raster/r.learn.ml2 failed

Does anyone know why it fails in the releasebranch_7_8 (Python 3.6)
pipeline but works in releasebranch_7_8 (Python 3.8)?

thanks
Markus