A workaround is to first remove all borders, and then re-apply the desired borders.

Repro
Version: 7.1.0.0.alpha1+
Build ID: c784b3da15102caf1022e83371863a86766e69cd
CPU threads: 4; OS: Mac OS X 10.12.6; UI render: default; VCL: osx
Locale: nl-NL (nl_NL.UTF-8); UI: en-US
Calc: threaded

Can't reproduce in 7.2.0.0.alpha0+ (e57665ea6f812aff9fc87073ce947f40a8b26e9d) / Ubuntu.
Not sure if it's fixed now or I'm missing something, are you applying table borders using the Table toolbar? Plus I'm assuming you're inserting the table via the dialog, and not the toolbar widget, which already adds borders.

Telesto, you set regression and bibisectRequest keywords, can you also provide a known working version number / hash?

Steps 2 and 3 are all done using the table property dialog, not the toolbar. In addition, by saying appling the borders I mean set the desired borders _and click OK_.

Created attachment 168351 [details]
Screencast (no repro)

I see. I'm attaching a screencast of the steps, and what I see as result.

No repro with
Version: 7.2.0.0.alpha0+ (x64)
Build ID: 315c7570c4a72f4c834086082825533b1e50d1bf
CPU threads: 4; OS: Windows 6.3 Build 9600; UI render: Skia/Raster; VCL: win
Locale: nl-NL (nl_NL); UI: en-US
Calc: CL

The issue is present with
7.1.0.0.alpha1+ on osx

Not sure if the fix got backported (didn't test 7.1b2)

(In reply to Aron Budea from comment #5)
I see from your screencast that you followed the wrong steps. 

Detailed Steps to Reproduce:

1. Insert a 2*2 table in Writer using "Table > Insert Table" menu.

2. Click the top-left corner of the inserted table, to select the whole table, then right-click and select "Table Properties". In the table properties dialog, apply borders to all cells by clicking the 4th pre-defined border style, then click OK. So the borders look like this:
----------
|   |    |
----------
|   |    |
----------

3. Right-click in the table and click "Table Properties" again; in the table properties dialog, remove the left and right borders, then click OK.

Current Result:
----------
|   |    |
----------
|   |    |
----------

Expected Result:
----------
    |     
----------
    |     
----------

Created attachment 168368 [details]
Screencast to Reproduce

Bug still exists if I run with 
SAL_USE_VCLPLUGIN=gen ./instdir/program/soffice

(as compared with gtk3).

Bug already existed in
Version: 6.2.0.0.beta1+
Build ID: 9df01c894d73e744a9d55c3db64f052a8f496287
CPU threads: 4; OS: Linux 5.9; UI render: default; VCL: gtk3; 
Locale: zh-CN (zh_CN.UTF-8); UI-Language: en-US
Calc: threaded

And may be even older, or even never worked. Could someone having the "releases" bibisect repo to test?

(In reply to Kevin Suo from comment #12)
It should be in the 7.1 branch.. far to many people would have noticed between 6.2-7.0.. So if it's present in older editions it's a local problem (profile?)

However I do believe it's in or was in the 7.1 branch

I can reproduce this on Linux with Version 4.1.0.0.alpha0+ (Build ID: efca6f15609322f62a35619619a6d5fe5c9bd5a) and 7.2 (SAL_USE_VCLPLUGIN=gen ./opt/program/soffice)

Created attachment 171481 [details]
normal behavior

Created attachment 171482 [details]
bug behavior

Doesn't look clear. 
Comment 0/Comment 8 is repro also in Windows, so hardly platform specific. 
Rather, difference is whether border click is 2 or 3 times (1 time is select).
Works with 3 times. Is it OK for you?
Only issue I have with this is: where's this documented? 

Comment 15 and Comment 16 is another issue, regression in 7.2+.

Per my previous comment, I change this bug to Documentation.
If you disagree, please explain.

Note that in Comment 15 and Comment 16 (which are another issue like bug 142165 or bug 142166) borders were removed with 3 clicks, which seems right, just needs to be explained.

(In reply to Timur from comment #18)
OK, now I see it. The same strange behaviour also exists in Calc. This is the first time I know how to apply borders in LibreOffice this way, having been a LibreOffice user for so many year. Apparently this must be extensively documented.

The intermediary gray state is used when you select multiple cells and some of them have different border formats.

From the Writer Guide 7.1, page 287:
https://documentation.libreoffice.org/assets/Uploads/Documentation/en/WG71/WG71-WriterGuide.pdf

"When the selected cells have different styles of border, the User-defined area shows
the border as a gray line. You can click the gray line to choose a new border style
(first click), leave the border as it is (second click) or delete the border (third click)."

The corresponding help page is:
https://help.libreoffice.org/7.2/en-US/text/shared/guide/border_table.html?DbPAR=WRITER

The help page opened via HID is:
https://help.libreoffice.org/7.1/en-US/text/shared/01/05030500.html

None of them mention how each click works and need an update.

Created attachment 171932 [details]
[VIDEO] All borders affected when only some cells are selected

In spite of the lack of documentation (which does need fixing), border formatting via Table Properties seems to be broken in LibreOffice. The Writer Guide says:

"If a group of cells is selected, the border will be applied only to those cells."

However, in the video I've just uploaded note how border formatting does not work as expected using the Table Properties dialog.

Interestingly, formatting using the sidebar works as expected.

I guess we're facing a border formatting bug here as well.

System info:
Version: 7.1.3.2 / LibreOffice Community
Build ID: 10(Build:2)
CPU threads: 16; OS: Linux 5.8; UI render: default; VCL: kf5
Locale: pt-BR (pt_BR.UTF-8); UI: en-US
Ubuntu package version: 1:7.1.3~rc2-0ubuntu0.20.10.1~lo1
Calc: threaded

(In reply to Timur from comment #22)
> Border to all cells instead to selected is regression bug 142165.

Timur, forget my question in the previous message. Only now I read the bug report 142165.

*** Bug 107679 has been marked as a duplicate of this bug. ***