Massive thanks to @dangcv
I made your recommended changes (see below) in woocommerce version 3.0.5 & again in version 3.0.6 & it’s temporarily fixed the issue, so massive thanks.
Was very disappointed it wasn’t fixed in version 3.0.6, but hopefully it will be fixed with the next update, but I’m definitely keeping these notes for next time.
Locate file:
wp-content\plugins\woocommerce\includes\gateways\paypal\includes\class-wc-gateway-paypal-request.php
Change from:
‘return’ => esc_url( add_query_arg( ‘utm_nooverride’, ‘1’, $this->gateway->get_return_url( $order ) ) ),
‘cancel_return’ => esc_url_raw( $order->get_cancel_order_url_raw() ),
Change to:
‘return’ => urlencode( add_query_arg( ‘utm_nooverride’, ‘1’, $this->gateway->get_return_url( $order ) ) ),
‘cancel_return’ => urlencode( $order->get_cancel_order_url_raw() ),
