1) Not all online store will give you the software, when purchasing the remote from them. And almost no one is going to supply you the software if you don't buy it from them. The software is large - 820MB. 2) The software IS complicated. If you are a DIY who has experience with programming remotes, then it isn't that bad. No experience? No chance you will figure this out anytime soon. 3) You can upload from the old remote. So just transferring the file to a new remote would be pretty simple.
Now your actual problem: This does NOT sound like a problem with the URC remote to me. It sounds like a problem with your cable box. Comcast commands get sent thru the cable box, to a cloud server, then back to the cable box to instruct it what to do. Very stupid idea they have been doing for many years now. Many times I have seen the original Comcast voice remote work fine (it works thru bluetooth) but the IR gets wonky. The clue about you sending many commands, then suddenly responds to all of them at once - points me towards the Comcast service that is the problem. You can try to have Comcast swap the box. If that doesn't work, then it maybe a latency issue with the service at your location. And there is nothing you are going to be able to do about it. Just use the Comcast remote for surfing and the URC remote for everything else.
I would say there is less then a 10% chance it is a problem with the URC remote. But hey, it does happen. But even if it is the URC remote, it might not be hardware related, but a bug in the programming. Meaning it would need to be reprogrammed from scratch - transferring the old program to a new remote, might just transfer the bug to the new remote.