The interview process until the last part was nice but the way they evaluated the technical challenge was weird and imho not just.
They asked me to recreate a part of their website which was made using jQuery, which I rewrote using pure JS, shortening it to ~400 lines of code from the original ~1600 and it worked faster than the original solution. They then said I "copied a lot of code from the original" by which they meant the ~10 lines of code which simply sorted an array.
I wrote them back explaining why I thought their evaluation was unfair and that I thought it was weird that they thought someone interviewing for a senior position wouldn't know how to sort an array and asked them whether they would reconsider, or in either case give me pointers on what I could do better. I got completely ghosted thereafter. They could've just said no and I would understand.