I can not modify admin note on client product page, ticket not created

[postcd]

Hello,

on WHMCS 6.3.2, legacy WHMCS 5 template
Apache Version     2.4.37
PHP Version     5.6.38

i made no modifications or adding any plugin or such and i found that i can no longer edit my admin notes field when editing client product (clientsservices.php?userid=x&id=y)

i am also unable to submit ticket for the client from within admin area, i select user id, but after submission it says no such ID. Also i can not submit ticket logged in as a client, ticket is submitted, i click its ID, and it says such ticket does not exist and it indeed is not in MySQL database.

i checked MySQL tables, they do not seem erroneous (i ran repair function of phpadmin on them).

i CAN modify my note about client on clientssummary.php?userid=123

Also stopped working e-mails (mailserver says dkim_remote_smtp defer (-53): retry time n0t reached for any h0st for 'gm@il.com') - but i hope this is unrelated.

i checked error_log files, enabled debug mode, checked browser dev Console no errors except that content security policy blocked loading of https://fonts.googleapis.com/css?family=Open+Sans:400,600 („style-src“).

Please kindly advice me what to check. Thank you