Voice incoming calls in Telegram are silent, how to fix it?

Question

iOS

Has anyone encountered a glitch when the call is not heard during an incoming call to Telegram. If the cart is open at the time of the call, just a notification is visible in the silence. If it is minimized or the iPhone is locked, it is generally not known that there is a call. Never seen this on other phones. I rummaged through the settings of the iPhone itself (do not disturb, notifications, etc.), in telegrams (compared point by point with known working settings from other devices). Deleted / set, received notifications of all notifications, allowed him everything, and again - the call is not heard. WhatsApp and others work great, but the cart doesn't work. No one has come across something like this? Maybe Telegram's voice communication is playing tricks?