You can easily see with the script above that the 1 year limitation and the slowness really exist. And it has nothing to do with 300 ticks. With 3000 ticks it would be not faster. When you claim you can download more years or faster with other software, then my first suspect is that you're simply downloading it in lower resolution.

Since it makes obviously not much sense to speculate here - if you think you have a technical issue, get to support. They do not read this forum. If it's a bug, help is free. And suggestions are free anyway.