Error on invoice creation - Hook->SequentialNumbering()

[mastly]

Hi,

We work with Katamaze Billing Extention for a while,  since few days and without changing version we get a validation error on every created invoice.

Invoices are still created although.

We changed invoice number variable and increment with same issue

TypeError: Cannot access offset of type string on string in /var/www/WHMCS/html/modules/addons/BillingExtension/core/BillingExtension_Admin/Hook.php:3893
Stack trace:
#0 /var/www/WHMCS/html/modules/addons/BillingExtension/core/BillingExtension_Admin/Hook.php(4523): BillingExtension\BillingExtension_Admin\Hook->Warnings()
#1 /var/www/WHMCS/html/modules/addons/BillingExtension/hooks.php(647): BillingExtension\BillingExtension_Admin\Hook->SequentialNumbering()
#2 [internal function]: BillingExtension_InvoiceCreation()
#3 /var/www/WHMCS/html/vendor/whmcs/whmcs-foundation/lib/Hook/Manager.php(0): call_user_func()
#4 /var/www/WHMCS/html/vendor/illuminate/support/Facades/Facade.php(261): WHMCS\Hook\Manager->run()
#5 /var/www/WHMCS/html/vendor/whmcs/whmcs-foundation/lib/Billing/Invoice.php(0): Illuminate\Support\Facades\Facade::__callStatic()
#6 /var/www/WHMCS/html/includes/quotefunctions.php(0): WHMCS\Billing\Invoice->runCreationHooks()
#7 /var/www/WHMCS/html/iitadmin/quotes.php(0): convertQuotetoInvoice()
#8 {main}

Does that ring a bell to someone?

Thanks

Mastly

 

[RadWebHosting]

I don't have any experience with this particular module, but the error is common when upgrading from PHP 7.x to PHP 8.x and typically is a difference in syntax or that you are incorrectly mixing string and array functions.