The authentication often failed

[Centaure13]

Hello,

I use Testlink 1.9.19.
Often, when I attempt to connect, the authentication failed.
I need to try many times to succeed.
Sometimes, it works the first time... sometimes, I need to do 5-6 tries.

The log not display any explanations which can help to understand.

Have you an idea ?

Thanks a lot

[fman]

What kind of authentication are you using? Native? LDAP?