The Tavern

My skill is at lvl 27, I can still select it to train it. What's going on here? I'm playing on trunk online.

https://imgur.com/a/DdZxsZD

Cross-training from slings, maybe?
The combined skill is 27, but the individual is not.

I also had this. As Sorcerous said, cross-training is responsible.
In general I think It'd be nicer if there was some kind of automatic training target at 27 skill.
If you're following Ash (or planning to switch to Ash) you can abuse it with Transfer Knowledge.

I reported this a while back as https://crawl.develz.org/mantis/view.php?id=11219, and I doubt I'm the first. I think this behaviour is by design. I don't like it; either it annoys the player by being a hidden way to waste XP, or it allows Hypothetically Optimal Man to build up "drain armour" in selected skills [1]. Neither seems like desirable gameplay.

On the other hand it would be odd if you could train (say) M&F to 27 with 29,750 XP then overtrain it by training Staves, but were prohibited from first training Staves then investing 29,750 XP in M&F, so a change to this behaviour would want a little thought. (Excess XP from crosstraining is just lost, to prevent "drain armour"? Interacts badly with Ru's sacrifice skill...)

[1] Of course thinking both these things at once suggests a certain confusion of ideas on my part.