lowercase letters are two byte instead of 1, so it is reading the 1st byte now the whole.
(might be a little off)
That's exactly it. TI-BASIC programs are stored as
tokens, not characters. Characters are always one byte, but tokens can be up to two. Lowercase letters in particular are two-byte tokens that have $BB as a first byte, and lo, $BB in decimal is 187!
I suggest you take a look at
this guide. In particular the $BB tokens are listed
here.