An add-on for fixable 'went wrong' things, to give hope...
With my DLA -> PIP, I had lots of time but asked for more, then asked for a reconsideration and had a deadline for that. The wotsits messed up and did the reconsideration before the deadline, probably because I'd sent them some info, just not all of it (and I did say I was sending more).
Fortunately, I sent my extra evidence signed-for, so they did another reconsideration, and to my surprise, I didn't actually have to ask them to. But for all that I feel like screaming when I think of DWP paperwork, they were good with me about extensions and re-doing their 'oops forgot the extended deadline' decision.
(Mind you, given the amount of paperwork I sent them, they were probably frightened I'd send more.)