PHP Fatal Error

I got these errrors in the error_log file after activating the WP SMTP Mailer – SMTP7 plugin, entering SMTP parameters and attempting to login to https://SITENAME.com/wp-admin. I use Admin Safety Guard plugin to send a One-Time-Password email message.

After clicking the Log In button, the next page (the OTP input page) never displayed. AFter a timeout, the error 504 page was displayed. Deactivtating the WP SMTP Mailer – SMTP7 plugin returned our website to normal behavior.

Stack trace:
#0 /home/SITENAME/public_html/wp-includes/class-wp-hook.php(341): wpmsm_mail_form()
#1 /home/SITENAME/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters()
#2 /home/SITENAME/public_html/wp-includes/pluggable.php(435): apply_filters()
#3 /home/SITENAME/public_html/wp-content/plugins/admin-safety-guard/app/Classes/Features/TwoFactorAuth.php(356): wp_mail()
#4 /home/SITENAME/public_html/wp-content/plugins/admin-safety-guard/app/Classes/Features/TwoFactorAuth.php(288): ThemePaste\SecureAdmin\Classes\Features\TwoFactorAuth->send_mail()
#5 /home/SITENAME/public_html/wp-includes/class-wp-hook.php(341): ThemePaste\SecureAdmin\Classes\Features\TwoFactorAuth->intercept_login_with_otp()
#6 /home/SITENAME/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters()
#7 /home/SITENAME/public_html/wp-includes/pluggable.php(702): apply_filters()
#8 /home/SITENAME/public_html/wp-includes/user.php(109): wp_authenticate()
#9 /home/SITENAME/public_html/wp-login.php(1323): wp_signon()
#10 {main}
  thrown in /home/SITENAME/public_html/wp-content/plugins/wp-mail-smtp-mailer/wp-mail-smtp-mailer.php on line 113
[14-May-2026 13:18:45 UTC] PHP Fatal error:  Uncaught TypeError: Cannot access offset of type string on string in /home/SITENAME/public_html/wp-content/plugins/wp-mail-smtp-mailer/wp-mail-smtp-mailer.php:113
Stack trace:
#0 /home/SITENAME/public_html/wp-includes/class-wp-hook.php(341): wpmsm_mail_form()
#1 /home/SITENAME/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters()
#2 /home/SITENAME/public_html/wp-includes/pluggable.php(435): apply_filters()
#3 /home/SITENAME/public_html/wp-includes/class-wp-recovery-mode-email-service.php(225): wp_mail()
#4 /home/SITENAME/public_html/wp-includes/class-wp-recovery-mode-email-service.php(62): WP_Recovery_Mode_Email_Service->send_recovery_mode_email()
#5 /home/SITENAME/public_html/wp-includes/class-wp-recovery-mode.php(185): WP_Recovery_Mode_Email_Service->maybe_send_recovery_mode_email()
#6 /home/SITENAME/public_html/wp-includes/class-wp-fatal-error-handler.php(55): WP_Recovery_Mode->handle_error()
#7 [internal function]: WP_Fatal_Error_Handler->handle()
#8 {main}
  thrown in /home/SITENAME/public_html/wp-content/plugins/wp-mail-smtp-mailer/wp-mail-smtp-mailer.php on line 113
[14-May-2026 13:18:54 UTC] PHP Fatal error:  Uncaught TypeError: Cannot access offset of type string on string in /home/SITENAME/public_html/wp-content/plugins/wp-mail-smtp-mailer/wp-mail-smtp-mailer.php:113
Stack trace:
#0 /home/SITENAME/public_html/wp-includes/class-wp-hook.php(341): wpmsm_mail_form()
#1 /home/SITENAME/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters()
#2 /home/SITENAME/public_html/wp-includes/pluggable.php(435): apply_filters()
#3 /home/SITENAME/public_html/wp-content/plugins/admin-safety-guard/app/Classes/Features/TwoFactorAuth.php(356): wp_mail()
#4 /home/SITENAME/public_html/wp-content/plugins/admin-safety-guard/app/Classes/Features/TwoFactorAuth.php(288): ThemePaste\SecureAdmin\Classes\Features\TwoFactorAuth->send_mail()
#5 /home/SITENAME/public_html/wp-includes/class-wp-hook.php(341): ThemePaste\SecureAdmin\Classes\Features\TwoFactorAuth->intercept_login_with_otp()
#6 /home/SITENAME/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters()
#7 /home/SITENAME/public_html/wp-includes/pluggable.php(702): apply_filters()
#8 /home/SITENAME/public_html/wp-includes/user.php(109): wp_authenticate()
#9 /home/SITENAME/public_html/wp-login.php(1323): wp_signon()
#10 {main}
  thrown in /home/SITENAME/public_html/wp-content/plugins/wp-mail-smtp-mailer/wp-mail-smtp-mailer.php on line 113