Bug in melt raising Error with dup columns as value vars
- [x] closes #41951
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

@simonjayhawkins I think this changed in May last year, so probably not woth backporting?
thanks @phofl 

this seemed simple enough > @simonjayhawkins I think this changed in May last year, so probably not woth backporting?

can confirm, first bad commit: [62c7dd3e771d5dc2921212cb363239b8f1447058] Fix MultiIndex melt when col_level is used (#34329)

This looks like it would be a straightfoward backport. I see no harm in backporting as it's a regression, but would need release notes moving first so that autobackports work. Meaning opening a new PR for the Whatsnew before backporting this? > Meaning opening a new PR for the Whatsnew before backporting this?

yes. @jreback thoughts on including this regression fix in 1.2.5? (it was a regression in 1.1) prob not worth backport to 1.2.x