Created attachment 151876 [details]
That file I created myself. It contains the section and the field - you can try starting from step 5.

reproduced on 

1. Windows10 LO version 6.2.1.2
2. Debian Linux Stretch LO version 5.2.7.2 (stable)
3. Debian Linux Stretch LO version 6.1.5.1 (backports)
4. Debian Linux Stretch LO version 6.2.4.2 (flatpak)

Steps to reproduce:

1. Create new document.
2. Menu: Insert->Fields->More fields
2.1. Tab Variable
2.2. Set variable
2.3. Format: general
2.4. Name: mycondb
2.5. Value: 2
2.6. Button "Insert"
3. Type some text and select it
4. Menu: Insert->Section
4.1. Section name for example mycond
4.2. Check box "Hide" 
4.3. In field "With condition" type in "mycondb LEQ 1"
4.4. Button "Insert"
5. Double click field mycondb and set value to 1

If section will disappear, then set field value again to 2 and then again to 1.

Result: section does not disappear, if you go to Format->Sections, you will see that condition text that we entered at the step 4.3 disappeared and there is only "0" there.

Expected result: section will appear and disappear, condition will not be changed.

Additional information:

attaching 2 example files.

File #1 test_section_condition_broken.odt That file I created myself. It contains the section and the field - you can try starting from step 5.

File #2 test_section_condition_working.odt - file with the section and field which is surprisingly working! The difference is that I do not created that file, but downloaded from the link on this page https://ask.libreoffice.org/en/question/132219/can-you-use-conditional-text-in-libreoffice/