Thumpnail problem

hi everyone,

i have some problems with thumbnail`s on my website,

we did not change any code ourself.

the problem,

we upload pictures of random sizes to our website,

and some pictures get a propper thumbnail but most of them dont,
they get cropped wrong,

of even the picture itself displays wrong on the website:(

but it all looks like cropping problems.

also when i go to editing a picture some pictures give the the ability to crop/resize thumbnails or the entire picture, i dont get this menu with all of my pictures:( any thoughts on wy i dont get it everywhere?

the website`s url is http://www.wijnvanremko.nl
its a wine selling website and all the pictures should be a full/whole bottle not cropped/cut off as most of them are now.

hope to hear from you soon