A bit late to the party, but I had a lot of issues with modifying LL back in September, it wouldn't let me change the times or rides at all. Similarly I could see that there were earlier times available for the rides than what was originally assigned, but the app would not let me change anything, even though there were no issues with overlapping times or ADRs. We've gone through this LL process for a handful of trips and I've never experienced anything like this before, usually I've been able to modify with ease. I ended up reaching out to a CM via the in app chat and they were able to modify the times to the earlier ones I was seeing, so that's always an option when the app is acting up. I've found for the most part the in app chat has been very helpful for LL issues. So yeah, long story short, don't forget about the in app chat!