The low volume is a red herring here. 3 to 5 chats a day can't trip a flood limit, so the ban is about trust and reports, not how many you sent.
A few likely culprits. First, the account itself. Half a year old sounds safe, but age alone means little if it was made on a virtual number, never warmed, no photo or bio, no real history. Telegram trusts behavior, not a birthday, and a cold thin account on a fresh Telethon session reads as a bot fast.
Second, the network. If Telethon ran from a datacenter or VPS IP, that's one of the biggest flags there is. A clean residential or mobile proxy matters far more than slowing down.
Third, and this is the real one, who you messaged. Cold first contact to people who don't have you saved is the highest risk move on the platform. It only takes a couple of report or block taps on a cold account to kill it, and a couple out of five lands easily. The driver is the report rate, not the count.
So slowing down won't save an untrusted account. What helps is warming it like a human for a couple of weeks first, a clean stable proxy, a real number rather than a virtual one, and spreading cold outreach across several accounts instead of leaning on one. Trust is earned by history, not by going slow.
Best,
Floqal