[SOLVED] Error on sending Emails

Hi,

When I look into my log file I have a lot of error messages like this one :

2020-04-10 08:42:05.545 ***** ERROR ***** [V8.4.2] ERROR *****
2020-04-10 08:42:05.545 ***** ERROR ***** [V8.4.2] on file '/var/www/html/projeqtor/tool/sendMail.php' at line (135)
2020-04-10 08:42:05.545 ***** ERROR ***** [V8.4.2] cause = array_flip(): Can only flip STRING and INTEGER values!

Doing some tests, I realise it is related to the submit work action. What could make this happen? I realised that even if I configured the options " after submit, alert to project leader " and "after submit, alert to team manager" to Email, those people never receive the messages.

Thank you for you help.
MCanuto