Error after password validation. Unable to continue

My site is made with WordPress and I use Passster to protect the intranet with a password.
Everything was working normally with the version 4.2.29
By automatically switching to the version 4.3.2, without changing anything, an error occurred. Upon validation of the password, a red rectangle appears under the Passster “validate” rectangle, which remains for a short time with the label inside “An error occured“; no error code, no other indication. To unblock the situation, I am obliged to disable Passster.

Important informations :
– in WordPress administration mode, the problem does not appear.
– the message is different from a password error that works normally, with the same type of red rectangle
– in normal user mode, the problem does not appear at first use after Passster activation, and disappears sometimes.

My mail : [email protected]

The page I need help with: [log in to see the link]