Omissions and phantom marks on printout

MuseScore 3.6.2; MacBookPro (Catalina); HP LaserJet Pro 400 (401dw)

The following problem has only recently begun to arise with my MuseScore files. When I print out MS files that are correct on the screen, the grand-staff bracket goes missing and there appear instead a few wispy smudges some of which resemble parts of the bracket shape. I've attached some images:

1. Screenshot of the correct original.
2. Photo of printout of that same file. Note the marks where the bracket should be.
3. Detail from the same photo.

Wondering whether the margins were too narrow, I tried increasing them (moving the left margin farther to the right) but that didn't fix the problem. I also tried replacing the bracket with an angle brace, and while that produced a correct brace on the screen, it too printed oddly. I then printed out a PDF of the original file, and something else went wrong on the printout: smudged treble clef.

4. Printout of PDF of original

Next I printed a correct Finale 27 version of the same assignment, and it printed perfectly. I was expecting that result, because I am not encountering this problem except when using MuseScore.

Finally, I tried printing the original MuseScore to a different printer, and it printed correctly.

The conclusion I draw is that MuseScore and my printer are not communicating properly, but how do I ascertain, without buying a new printer (because it works great with every other application I use), whether the problem lies more with one than the other.

I'd be grateful for any suggestions. Thank you.

Gene