Besides little long time bugs (like my device prompting for password because it's been 48 hours since last TouchID when it's actually been like 8) there are bugs in new things.
Since 9.0 (or so) using CarPlay I find that it occasionally messes up the audio engine on the phone requiring a restart to a fix. That means instead of my old weeks and weeks of uptime it now varies between 24h and 7d or so.
Having your phone not have audio work correct? Horribly obnoxious. Especially when 70% of what you do is listen to music and podcasts.
I gave up on Podcasts and switched to Overcast because Apple (despite years) was unable to correctly sync which podcasts I'd listed to and which I hadn't. I'm wary to buy things from iTunes because I end up with 2 or 3 copies in my library of some songs, randomly.
I STILL randomly get corrupted songs on my phone and occasionally have to reload all 45GB of music (everything I own, just easier since I have the space) to fix the issue. Don't know why.