Trendyol Elite Member Installment Error - Installment Option Disappears

I’ve been shopping on Trendyol for years and I’m an Elite member. However, for the past couple of days, even though some products show a “3 installments at the cash price” option, the system doesn’t allow me to complete my purchase when I select it. When I tried paying in a single installment, the purchase went through immediately. I asked my friends, and they’re experiencing the same issue. I feel that my rights as a customer have been violated, and I’m filing a complaint about this situation.