unable to push: remote: fatal: bad object HEAD

Suddenly:

> git push                                                                                                                        

Counting objects: 62, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (41/41), done.
Writing objects: 100% (62/62), 6.08 KiB | 0 bytes/s, done.
Total 62 (delta 47), reused 27 (delta 12)
remote: fatal: bad object HEAD
fatal: bad object HEAD
To git@gitlab.com:xcontest/xctrack.git
 ! [remote rejected] jarda-splashscreen -> jarda-splashscreen (missing necessary objects)
error: failed to push some refs to 'git@gitlab.com:xcontest/xctrack.git

tested against different branches from different clones...

> git fsck --full                                                                                                                 
Checking object directories: 100% (256/256), done.
Checking objects: 100% (23565/23565), done.