"! Undefined control sequence. <argument> \fail" after update. But what package?

[Ulrike Fischer]

Am Thu, 6 Jan 2022 14:27:05 +0100 schrieb Alexander Krumeich:


> I'm perfectly aware that this error description is far from ideal. I'm
> sorry I can't provide an MWE here.

As your document errors in the preamble, providing an MWE is really
easy. At least provide the full log until the error so that one has
at least a chance to identify the package.

-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/