Blogs with large numbers of posts (over ~5000 posts) will find this most noticeable. The app uses the Tumblr API which has minute/hour rate limits. When the site is busy we sometimes hit this rate limit. Please be patient or come back again later. If the problem persists please send me a message using the link below.
The app is hosted in the UK so if you are based far away (e.g. USA, Australia, etc) it may run a bit slower due to latency. Don't worry, please be patient.