This error message is being written to the logs on our website every few seconds. Redacted version here, full version in a private note.
The server is running PHP 7.4, WordPress 5.5.3, and a child version of Pro theme version 3.2.3.
[Sat Nov 14 17:29:14.997174 2020] [proxy_fcgi:error] [pid 6740] [client 181.171.132.74:45808] AH01071: Got error 'PHP message: PHP Warning: A non-numeric value encountered in /home/[redacted]/[domain]/wp-content/themes/pro/framework/functions/frontend/generated-css/renew.php on line 131PHP message: PHP Warning: A non-numeric value encountered in /home/[redacted]/[domain]/wp-content/themes/pro/framework/functions/frontend/generated-css/renew.php on line 135', referer: [domain]