Issue with Hook.php and Stripe

[Bodoh]

Hello all,

 I'm using Katamaze - Billing Extension but I'm getting into an issue when trying to test the order flow after the payment.

 Details:
 - WHMCS version 8.7.3
 - Billing Extension addon latest version 2.2.181
 - Stripe with "Test data" mode enabled.

 Error after completing a payment (tried with a new credit card and also with the same saved):

TypeError: Argument 2 passed to BillingExtension\BillingExtension_Admin\Hook::Warnings() must be of the type string or null, array given, called in /home/user/mysite/modules/addons/BillingExtension/core/BillingExtension_Admin/Hook.php on line 4397 and defined in /home/user/mysite/modules/addons/BillingExtension/core/BillingExtension_Admin/Hook.php:3755
Stack trace:
#0 /home/user/mysite/modules/addons/BillingExtension/core/BillingExtension_Admin/Hook.php(4397): BillingExtension\BillingExtension_Admin\Hook->Warnings('gap', Array, 'Automatic')
#1 /home/user/mysite/modules/addons/BillingExtension/hooks.php(687): BillingExtension\BillingExtension_Admin\Hook->SequentialNumbering('set', 'Invoice', 35, false)
#2 /home/user/mysite/vendor/whmcs/whmcs-foundation/lib/Hook/Manager.php(0): BillingExtension_InvoicePaidPreEmail(Array)
#3 /home/user/mysite/vendor/illuminate/support/Facades/Facade.php(261): WHMCS\Hook\Manager->run('InvoicePaidPreE...', Array, false)
#4 /home/user/mysite/includes/functions.php(0): Illuminate\Support\Facades\Facade::__callStatic('run', Array)
#5 /home/user/mysite/includes/invoicefunctions.php(0): run_hook('InvoicePaidPreE...', Array)
#6 /home/user/mysite/vendor/whmcs/whmcs-foundation/lib/Billing/Invoice.php(0): processPaidInvoice(35, false, Object(WHMCS\Carbon))
#7 /home/user/mysite/cart.php(0): WHMCS\Billing\Invoice->addPayment('19.90', 'txn_3NXSgIDxLmL...', '0.85', 'stripe')
#8 {main}

 Did anyone hit the same error? Or any ideas here?

I can't look into "hook.php" file as is IonCube coded, so I don't know what is trying to do. 

 

Thanks in advance!
Bogdan

[Bodoh]

Looks like the issue is coming from:

Warnings('gap', Array, 'Automatic')

Somehow Billing Extension is detecting a gap in the invoices but I can't find where is the issue as I've reinstalled a fresh instance and after the first order I'm getting in the same error.

Looking at the DB tables everything looks fine.

tblinvoices

The IDs are concurrent.