Why does the copy and pasting of a text into a search engine not always work lately?

I have run into this sort of thing before. I don’t know if you are facing the same problem.
Apparently some sites have sneaky embedded Javascript that somehow prevents a person from correctly copying from the site. IIRC the trick I heard discussed was something like an onClick() that changes the string as it is highlighted. The symptom was that the string when pasted was not the one expected. It sounds like you are experiencing a somewhat different problem.

Thanks @koanhead your answer wasn’t under my “new activity” .
I don’t know, I hope it stops happening. Otherwise it is impractical.