Vandalier cannot be leveled up normally, only through chests

[Dark]

Not sure what triggered it, I'm in a run in Cappella Magna and leveling up simply does not offer an option to level Vandalier, it thinks there's nothing and I only get the gold or chicken options. Chests still level up Vandalier

Level 119, level 4 Vandalier
https://imgur.com/8ygk8hg

Level 121, still level 4 Vandalier
https://imgur.com/dlsdP1O

End of the run at 136, found 1 chest to level it to 5
https://imgur.com/GFDDvM2

It's not banished (you can see no red square highlighted like Torrona's Box has), you don't get that many skips either, the option was simply never offered

[Iced_Paper]

This happens if you leveled everything else before getting all the levels for your evolved weapons (Vandalier).
It should be a bug, but this is really consistent. Once i even got the option to get levels for it after getting a Candybox from a chest, giving me a new weapon to level. So on the next level up i had the choice of Vandalier once again.

[Aristocratic Cthulhu]

Did you per chance get a hold of Vandalier via a Super Candybox?

[Lu2]

yeah happends to me also but it eventauly fixed by itself by reciving extra weapon from candybox later

[DeFragged]

Can confirm this happens and can 'resolve' itself if you find a weapon in a chest (in my case, it was upgrading a weapon that made it show up in my level up list again).