Davinci Resolve is definitely my favourite NLE to use now, but it does come with it's fair share of weird bugs and behaviours. Luckily none of them are as game breaking as Premiere Pro's painful crashing.
Black borders on imported images is a strange one that can be fixed playing with the image scaling options, if you have other image scaling in your timeline this could have an affect on them too though so make sure to check everything before you export it!