LO 7.2, OSX 10.14.6
I use a:
NN [tab] heading text
format. For no apparent reason the length of the tab space has increased and sometimes the text is shunted down onto a line under the heading number. There’s no apparent difference between heading levels 2 and 3 that suddenly acquired this problem and heading level 1 that doesn’t. Even stranger, the effect has only occurred to headings I’ve just been working with, not the rest.
Without any technical detail it is impossible to answer the question. Please edit to mention OS name and LO version.
Usually this kind of problem occurs when the number overflows the space allocated for numbering (e.g. from 9 to 10) or when your tab stop is too short and you skip to the next automatic tab.
Your best option is to attach a sample document exhibiting the problem. Thius means the styles must be the same as in the faulty document and settings for Tools>Chapter Numbering are also the same.
You are right, it was inadequate space for the number.
Thanks,
Stephen