Thanks @guarom,
And in:
- Help > About info
Can you press the “Copy” button + Paste it here?
That will be better than having the version+build# hidden in your screenshot.
Much easier to debug or search if all the version info is pasted as text. 
I think this is an issue from LibreOffice core. I don’t know the exact cause, but it seems like this bug got introduced very recently.
2 weeks ago, someone had very similar problems on the LibreOffice subreddit after upgrading to a recent LO 7.5 version:
His screenshots look almost exactly like yours! Where:
- The underline only goes most-of-the-way-under a word, then cuts off.
In my testing of your ODT, it looks like this:
- Only occurs at certain zoom levels.
If I’m zooming in-and-out, you can see the underline acting very oddly, stretching/shrinking beyond the words too.
This is my LO information:
Version: 7.5.5.2 (X86_64) / LibreOffice Community
Build ID: ca8fe7424262805f223b9a2334bc7181abbcbf5e
CPU threads: 8; OS: Windows 10.0 Build 19045; UI render: Skia/Vulkan; VCL: win
Locale: en-US (en_US); UI: en-US
Calc: CL threaded
Edit: It looks like it might be this exact bug!
- 156681 – The underline line in Writer doesn't match the length of the sentence, even in simple cases
Looks like it happened between LO 7.5.4 + 7.5.5, so it happened within the last month!
Exact cause isn’t found yet, but I would follow that LibreOffice bug report and wait for the fix.
Once the fix gets into LibreOffice, it should get pushed to Collabora Office soon after as well.
Edit #2: I submitted your document + some screenshots to the LibreOffice Bugzilla.
Thanks so much for the document + report, @guarom !
It’s okay here.
There is no specific “Collabora Office” (Desktop) subforum, so this User Support section works.
In the future, if there are many Collabora Office questions, then those can be split into their own separate section if needed.