(I've replied directly to this user via a ticket, for reference here is what I said):
There is a variable which can be set in your init.org, org-remove-property-drawers-from-render-output. By default this is turned on. I'll look into what the issue is here that's causing these to appear in your export.
I use clocking a lot, which makes export very messy.
Is there a way to exclude :LOGBOOK: and :PROPERTIES: from Export (one hack I found is to remove these lines from my org file and make a copy without those lines, but it's a bit ugly)