[DrChiper]

When starting "Read aloud" on a fresh page, the first part of the chapter text is almost always omitted. In the case here that is "TEST:". Irregular only the last few letters are read.
Subsequent headers are fully read as they should.

A further finding is that right after any ":" it would be preferred to have a certain delay (like as is used at the end period "."). This will sound more natural.