itunes says there is not enough space on ipad to sync selected music, but there is…

I'm just trying to sync my music - itunes on computer to itunes on ipad. I've done this before with both devices.

I have recently updated to the new itunes on my desktop and on my ipad (v.12.3)

I wanted to update my music on my ipad, so I plugged it in. Capacity bar says I have approx. 11GB available. Great.

I Select songs because I know my Entire Library would be too much.

Got a message asking if I'm sure I want to sync because it will erase everything currently on my ipad. That's weird, but guessing something odd, it thinks everything is new because I updated the itunes. Fine. It's all the same stuff anyway, was just adding a few new playlists. So I hit OK and sync.

Got a message saying it can't sync because I don't have enough space. As I mentioned, capacity bar says I have approx. 11GB available.

I tried a few more times, after unselecting a couple playlists (which I shouldn't have to, considering the small amount in total). Every time, the message said I needed a different amount of space, 5 GB, 3.32, 1. something. Always a different number. As I mentioned, capacity bar says I have approx. 11GB available.

So, what's the problem here? I can't sync my ipad anymore no matter what I do. Even though it has space.

I have 30 apps, no videos or shows, less than 1000 photos and have 1200 songs. I was actually trying to sync a fresh total of only 411 songs. Should not be a problem if I previously sync 1200.

???

Another super basic task made impossible by Apple.