The window frame is bulging. What is that?

That's what he means. That is a bulge because on the right side of the picture the edge already starts to move upwards again.

Window frame is bulging.
...
my sliding door has a bow downward.

So now:

Is it the door (leaf) that is bowed or the frame
(straightedge)

That it sounds hollow in places is normal, depending on the construction

Has it always been like this (installation error?) or only recently (wood core warped)?
Are the screws in the frame (across the reveal) possibly screwed in too tight or loose?

Does the door leaf stick when closing?
Does it close at the top earlier/later than at the bottom (mounted twisted)?

Hi,

the photos are nice to look at, but largely worthless without a reference (=ruler). Yes, something seems crooked in the photos. But whether that comes from reality or is just a distortion caused by the phone lens, God only knows. Especially with close-up shots, even high-quality lenses tend to distort. A phone snap usually has lenses of glass shard quality, and the images are then "straightened" again. That then has little to do with reality.

So do yourself a favor and hold something really straight against it, preferably with a spirit level.

Best regards,

Andreas

We had something like that a few days after the installation of the windows because the window fitter installed them too "tightly". The windows were then replaced.