I have a lot of output, and the compile output pane shows interleaved stdout and stderr. It looks like the buffer is flushed after a fixed character count (4096?), even in the middle of the line, which leads to partial results in the issues pane.

Example:

... much stdout here ...

The initial red part has 4,093 characters, then stdout 14,687 chars, and then stderr 4,092. It looks like this buffering only happens for stderr, stdout always shows full lines before switching to stderr.