This problem exist in LibO 3.4.4. and 3.4.3/
Step to reproduce.
1. Open Writer document.
2. Activate nonprinted character (View -> Nonprinted character)
3. Print document
4. Nonprinted character is invisible in screen now.
CONFIGURATION: Formatting aids - displayed nonprinting characters become unchecked during printing and PDF - Bug 40482
*** This bug has been marked as a duplicate of bug 40482 ***