Warning! By going through DOC, you damaged your document structure. The converted back to .odt is not the same as the original .odt. In particular, all page, character, frame and list styles are wiped away and replaced by direct formatting. So, it is up to you to decide if you accept a polluted and damaged document or if you want to keep on working with versatile and powerful styles.
You must weigh seriously the pros and cons. Personally there are more cons than pros. Reconsider deleting the sections, even if they are numerous (and if they are numerous, this means you have numerous sub-documents; in this case, I’d question the relevance of the number).