Generating a TOC, Sigil removes spaces from titles

Hello,

I haven't seen this before. Trying to generate a TOC from headers, Sigil is removing spaces in the titles after commas and periods. This particular TOC, a reference work, will have almost 4000 TOC entries, which I'm not sure if such is too much. Maybe that's part of if; if such is allowed – I don't see anything in the spec –, it's preferred.