Even when you import a template in Impress, you will find some weird bugs, like a slide insisting that it won't show the slide number. I found such random weird behavior that I wouldn't even know how to file a bug report for it, because they are impossible to reproduce.
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I know the stuff is built on top of some very ancient code. Sometimes I wish they would throw it all away and start from scratch in a modern managed, type safe language. It would be feasible if you forego backwards compatibility as I suppose a lot of the bugs have to do with trying to support the MS Office bugs. A consistent finding is that LO supports older office documents better than MS office itself.