Unknown: function '/' not found or invalid function name

Where is this error located?

Error appears in Demo and in newest update.

2021-11-25 01:59:28 [987d0d4f] - *** WARNING *** Array
(
[Error Msg] => Unknown: function '/' not found or invalid function name
[File] => Unknown
[Line Number] => 0
[Error Type] => E_WARNING
)