I'm not a 100% sure but I think Sigil's ePubTidyTool plugin might have an option to fix broken paragraphs ==>>
https://www.mobileread.com/forums/sh...d.php?t=264378
If you have access to recent MS Word you could try opening the PDF in it, and then you can use
Toxaris's eBook Tools MS Word add-in which has specific tools to help with PDFs. This add in can also create the epub - the code it generates is generally considered to be much 'cleaner' than other Word to epub converters, I believe some people use it for that feature alone.
Another useful Word add-in is
TransTools for Word / About (not free) which has some specific PDF cleanup features. It has a fair degree of overlap with the other one, but if you're doing a lot of PDF->EPUB it has a couple of things the other one doesn't.
BR