Scrolling issue

[guninia]

I've integrated the AFOpenFlowView into my project and works fine,
but when I stop running, and simply change the "openFlowView.frame.origin.y" value, the weird thing happened.

For example,
First, I set the frame as follows:
AFOpenFlowView *openFlowView = [[AFOpenFlowView alloc] initWithFrame:CGRectMake(0.0, 50, self.view.frame.size.width, 200)];
everything works fine.

than I set the frame as follows:
AFOpenFlowView *openFlowView = [[AFOpenFlowView alloc] initWithFrame:CGRectMake(0.0, 200, self.view.frame.size.width, 200)];

I can only scroll the cover in a small area which is 50 points height from top of the openFlowView.

I've tried several y value to test it, and it seems that there would be a boundary at y = 250, which I set for the first time "y = 50 and height = 200". The bottom position of the openFlowView is 50 + 200 = 250.
Only the area higher than y = 250 and lower than current openFlowView top position is scrollable.
That means, If I change the openFlowView y value larger than 250, I can't scroll it any more.

Here is my code:
startY = 50.0;
AFOpenFlowView *openFlowView = [[AFOpenFlowView alloc] initWithFrame:CGRectMake(0.0, startY, self.view.frame.size.width, 200)];
[openFlowView setDataSource:self];
[openFlowView setViewDelegate:self];
[openFlowView setNumberOfImages:[categoryArray count]];
for (int imageIndex = 0; imageIndex < [categoryArray count]; imageIndex++)
{
UIImage *image = [UIImage imageNamed:[[categoryArray objectAtIndex:imageIndex] objectForKey:@"imageName"]];
if (image == nil)
{
image = [UIImage imageNamed:@"Placeholder"];
}
[openFlowView setImage:image forIndex:imageIndex];
}
[openFlowView setSelectedCover:([categoryArray count] / 2)];
[openFlowView centerOnSelectedCover:NO];
[self.view addSubview:openFlowView];