You'll be fine, they value order metrics way too much to ban anyone. I don't think anyone's requested more refunds than me and I'm granted a refund nearly once every two days.
The way you request a refund makes a difference. Spillage, missing items, wrong items, contamination are the easiest. If you can prove the problem was with the delivery person or restaurant, then it's easier to get a refund. I'm assuming it's because they can penalize one of those two.
Persistence sometimes helps, today their automated systems offered a refund of Rs 26. Escalated to customer support and they offered 46. Asked them to check photos and they then offered 103. Item was 129 before coupons. This was for portion size, which is difficult to get refunds for.
Persistence can also lead to the customer support person giving up and asking you to email, in which case there is almost no going back and you have to email. I've been able to refuse to email and get an immediate refund just once in the last 5 years. So it's possible but incredibly difficult.
Zomato is a lot more stubborn about refunds. But their algorithm is far more flawed so it actually costs them more money because they will automatically approve a four digit refund if you're averaging less than X number of refunds per month (don't know the number exactly but mine is 1 per month with zomato for the current quarter).