Thanks Junpeng, this disappeared when updating.
Using pip, I reinstalled from git, which solved the issue. Sorry, I had briefly checked that I was up to date. Having installed a while ago, that was apparently with the pip repositories and not with git.
Also, regarding my other question, I discovered your presentation and the part on multivariate statistics and will try to work through it. There are lots of tricks in it that will certainly apply to my data.
Best,
Falk