This last bug has actually been introduced and fixed before. It affects mostly content in tables (as far as I could figure out). Some content put in the "old" tables is rendered in a weird way. In my case I'am sifting through hundreds of notes now without useful images and text. Web client seems fine though – this is the first time I use it over the Mac app.
There are also some minor elements of the web clipper (in this case the YouTube clipping feature) that are not put in the final note: The horizontal line below the thumbnail, the font, the font-color. But I guess that's something everybody can live with and is not related to release 6.13. Let me mention though that these elements where visible in earlier versions – which made the clippings look a bit more polished.
Lastly, and I hope this will be addressed, I will say that these unfortunate bugs in the areas of sync, formatting and stability seem to come up again and again – I can only talk Mac and iOS app though. See I'm passionate about the software, and IMO the Mac UI improvements go in the right direction. However, it seems there are some underlying problems. Perhaps the guys of the Mac Dev team are understaffed, or have unrealistic release schedules, or use a testing process that lacks coverage of use cases. For the latter: I can only recommend to employ as much automatic/regression testing as humanly possible and invest the time to make sure the release-quality will improve – before adding new features. The software I use that does this, introduces very few bugs in the core feature area on new releases. Perhaps something to contemplate.
For now I'm at the level where I think twice before updating to the newest versions. But i'm confident that this can change again soon – if you guys step it up a bit.