fatal: Authentication failed with GKR-message: received an invalid, unencryptable, or non-utf8 secret

[DEMODDIE]

failure_git_cred_mgr_with_logging.tar.gz

Host-OS: Ubuntu 16.04 x64
Java: 1.8.0_201
GIT: V 2.21.0
Test scenario is cyclic operation (see attached script tfs_git_test.sh): git clone of a repo (hostap e.g), delete the local work copy, wait 10s, do again
After a varrying timespan of 10 - 30 min. a failure occurs:

BaseSecureStore::readCredentials
Getting Credential for git:https://debrutfsq.de.eu.sew
Gkr-Message: received an invalid, unencryptable, or non-utf8 secret
Gkr-Message: call to daemon returned an invalid response: (null).(null)()
Could not retrieve secret from storage.
Return code: 6 description: Error communicating with gnome-keyring-daemon

To recover from this situation you must enter the credentials by hand again. This is not acceptable for automated night builds we want to use the git credential manager