Probably the most egregious behaviour is declaring different terms and conditions for sales and pre-orders after a person has handed over their money, particularly changing the terms around refunds. Literal Vader "pray I do not alter it any further". And illegal. Refunds in general have been a nightmare for customers with many making a complaint to the Attorney General of California which seems to have been the only way to get money back.

Check r/purism on Reddit if you want to see lots of examples of their shady behaviour.

Also: https://www.phoronix.com/news/Zlatan-Todoric-Interview

And: https://jaylittle.com/post/view/2019/10/the-sad-saga-of-purism-and-the-librem-5-part-1