It’s F1 on an external keyboard that does this (and Fn+F1 on the main laptop keyboard also leads to A). It seems to be a general Julia REPL thing btw, happens without TerminalPager loaded too. Searching it up, I found an old obscure issue Function keys i.e. F5 and F6 input random characters on windows console · Issue #28799 · JuliaLang/julia · GitHub so it looks like this has been this way since Julia pre-1.0 days!
There’s a lot going on in julia/stdlib/REPL/src/LineEdit.jl at master · JuliaLang/julia · GitHub and I’m guessing somewhere in there, some part of the input codes generated for F1-F5 keys on Windows is getting gobbled up, leaving only an A (or B C D or E) behind - probably something unintentionally written with Linux assumptions early on.