Just to inform and update other people on this, the product had been picked up by Delhivery on 20th of October. However, there was no movement till 30th of October. At this point, I raised a complaint and asked for an update. They responded saying they will update me in 48 hours. They didn't do this obviously and 3 days later (1st November) I again asked for the status. They replied saying they have raised an inquiry and will update me of the status. On 3rd Nov I raised another complaint since there had been no change in status. I received a response asking me to be patient.
This above response was sent again on 6th of November, asking me to be patient. Meanwhile, on 5th of November, I refunded the amount to the buyer since it was looking like the product would not get delivered. After this, I was travelling for a while and forgot about it and didn't follow up. There was no email from Delhivery themselves.
I returned home today and checked it again. The order was not showing on my direct.delhivery.com account at all. They had removed the listing even before the product got delivered. When I checked the status using the AWB number, they had removed all the original statuses and showed it as received at Bangalore as of yesterday. The fact that it was delivered after a month cannot be seen on their tracking page at all at this stage.
Anyway, it was showing as out for delivery. Around 11 AM I received a confirmation from the buyer that he has received the package and he will be making the payment again.
My experience with Delhivery so far was fairly good. However, just as is the trend these days, I found that if and when something goes wrong, there's no way to contact anyone other than raising a ticket, on which they have the complete liberty to not respond if they so please. So if everything goes smoothly, you're fine. But if they mess up, don't expect a satisfactory resolution.