InDesign 18.5 on Mac
Providing the steps would involve too many specific formatting choices, so I'll just describe what I'm seeing instead. I have a two-column text box for endnotes (literal; not InDesign-generated. E.g., "[tab]1.[tab]Note text."). I want the descriptors to align on the decimal point. When I use a decimal tab, the following text breaks like this:

[tab]6.[tab]Paul Renouard, Docteur Char-
cot, cover of...

The width of the text frame, however, will clearly accommodate "cot, cover." If I change the decimal tab to a right tab (and adjust its placement slightly so that the period is in almost exactly the same place), the line reflows as

[tab]6.[tab]Paul Renouard, Docteur Charcot, cover
of...

I've checked hyphenation settings, justification settings, and so on, but nothing will let the line rebreak as it should EXCEPT changing the decimal tab to a right tab. In fact, even if I try to a single letter after "Char" with the tab set as a decimal, InDesign forces the letter to the next line when it will clearly fit on the first line. Attached are two images showing the difference.