It was probably a glitch, because I can’t reproduce it now, or maybe something specific needs to happen for it to behave like that. Basically, as you can see, the 3 ticks were rendered as text, inside single ticks, hence the dark background. Then the second time I would add 3 ticks, right underneath the previous one (the 3 ticks rendered as text inside digle ticks), it would then create the code block as expected. Hope it makes sense now?
I also just noticed that markdown in rich text mode doesn’t work as expected. Look at this where the single ticks are not affecting the text `test`, but the 3 ticks are doing their job.