patcher window elements

We have a patcher that behaves badly on Macs. The original patcher is very complex but I have isolated the problem in a smaller patcher with only a few objects. When you open it, the patcher does not have title window, nor menu, nor scrollbars, nor toolbar, etc. Is a clean rectangle. On the top there are two messages, one that makes the patcher smaller and one that makes the patcher larger.

The problem appears when making the patcher smaller: the position of the patcher window changes by going up a bit.

There are two other messages if you want to add/remove the windows title, etc. If you add windows title and so on, the patcher behaves well on both large and small windows sizes.

Any clues why without title bar and so on, the patcher goes up a bit?

Thanks!