This happens since v 5.4.x has been released. Not in v. 4.x. Let say you have copied a text with several paragraphs, and are going to paste it in a Writer document, no matter of which the insertion point paragraph style is (default text, heading1, quotation), all the pasted text paragraphs now get the style aforementioned; not even respecting the rules of the "following paragraph" for that style. So if you paste a text with one line paragraph, followed by several others, which one you would takes heading1 style, and the others get the rule of the "following paragraph" style (for heading1 style this should be default style), you'll get instead all heading1 style paragraphs.
*** This bug has been marked as a duplicate of bug 112511 ***