I see the problem as well using very latest org source code, i.e., this change
* 2020-07-06 12:05:18 +0200 07a4a7286 Nicolas Goaziou list: Fix regression when inserting items I created two long lines separated by a blank line. Each long line was created by typing "0 1 2 3 4 5 6 7 8 9 " then repeating it 7 more times. There are multiple problems. 1. Select both long lines and the blank line in between. M-q fills the first line but not the second one. 2. Select only the second line. M-q fills the first line, i.e., the line that was not selected! It does not fill the second line. 3. The problem occurs whether the long lines are delimited between #+begin_src ... #+end_src or not. 4. Select only the first line. M-q does nothing! 5. Select first line plus the following blank line. M-q fills first line. 6. The problem occurs for normal emacs mode as well vim mode within spacemacs.