Matt, I just found out about Arc Timeline Recorder (I already have Arc and Arc Mini).
So I downloaded it: it asked me for location access (I said yes), then it asked me for motion access and I clicked “yes”, and it crashed immediately. if I open it, it immediately crashes — so badly that after the crash it’s not even present in my app switcher.
So I deleted it, redownloaded it…exactly the same.
What’s up here? Thanks!
Ok so you’re the second person so far to see this happen! And the other person… isn’t me. So I have no idea what’s going on 
The good news that for the other person who was having this crash happen, it went away on its own a few days later.
Without any evidence for the cause, unfortunately the only (probably useless) advice I can offer is to try restarting your phone. Other than that… hope that it goes away on its own in a day or two.
I’ve had a poke around the crash reports in Xcode, and nothing useful is showing up there yet. But if it keeps happening, then I’ll … well, I’ll have to figure out something 
Yet another case of investigating a mystery with zero clues to go on. Such is indie developer life sometimes.
An update: mysteriously, after a few days, mine is opening just fine now too.
No clue what happened but glad it’s figured itself out!
One note here - Arc Recorder (now that it’s working) is giving me the permanent blue location services indicator in the Dynamic Island (which is obviously annoying and useless)…but this never happened with Arc and Arc Mini both installed and with “Always Allow” location services.
What’s different about Arc Recorder?
Ok this is a sore point. Heh.
The difference is that Arc Recorder is using the newly rewritten LocoKit2 recording engine, which replaces the 10 years of cruft that’s built up in old LocoKit (that Arc Timeline and Arc Mini use). LocoKit2 is written to use only the most modern coding techniques and most modern APIs, which mean that it uses iOS’s location recording functionality through the latest APIs that Apple have provided, not the extremely old APIs that old LocoKit uses.
The catch there is that Apple really don’t want apps to be able to turn off that Dynamic Island location indicator, so they’ve entirely removed that option from their new APIs. It’s just not there for LocoKit2 to use at all.
Apple have also been progressively making it more difficult to turn that indicator off each year, with various conditions and rules applied, both documented and undocumented. Back in one of the iOS 16 updates for example they made an undocumented change that required apps that turn off the indicator to not use the most energy efficient approaches to location recording. Utterly nonsensical! Oh, they didn’t tell anyone about that by the way - apps just started breaking, with no explanation at all. Nice.
Which is why in Arc Timeline’s settings views there’s an option to turn the indicator back on, to allow Arc to record more efficiently and use less battery. Now, if you think that Apple tying that indicator to energy/battery efficiency is crazy and makes no sense… I strongly agree. But it’s not like we can argue with them about it 
So yeah, even if I modified LocoKit2 (and thus Arc Recorder) to use some of the old APIs so that it could turn off that indicator, it would still mean that turning it off would result in worse battery life each day.
… I struggle to say nice words about this situation. It is painfully dumb, and I frankly just want to scream at Apple, calling them nasty words. But yeah, it is what it is.