Personally, I have only positive impressions from the "cooperation" with InPost - everyone can stumble, I haven't had it yet.
My friend is unlucky though

Once it happened to him that a strange woman calls him and informs him that she has his package. How? Well, she came to send the package, clicked through what was needed on the terminal, the door opened, and there was a package for a friend ... She took it, put hers on and was decent enough to call the friend (the phone number was on the address sticker).
The second story is a bit more interesting - this friend had a cash on delivery package - the download amount is a dizzying PLN 0.2. It is impossible to pay with a card at the terminal (transaction rejected), it is impossible to pay via the mobile application (an error occurred), the consultant suggests that the bank may be blocking such small payments/transfers (the bank claims that it is not true); the only option - go to the InPost headquarters (the other end of the city) and pay a dizzying 2gr. It is not possible to increase the download amount (maybe 1 PLN would pass?), suggestions to leave the cache in the locker did not meet with the consultant's favor. The package finally returned to the addressee.