Are your pictures stored in SD-card on your phone or Cloud service? This could be the reason why the opening gallery might be a bit slower when adding a picture on New Post view. Sometimes the reason might be also if your memory is running out.
- Try to save pictures locally on your phone
- Clean your memory/storage on your phone
- Try restart Hookle App.
- If it does not work you can also try clear memory/cache of the Hookle App