Can't add texture to anything

I downloaded the lastest MCreator version for mc 1.12.2 today and got it to work. I can edit my still empty mod by adding a block, and naming it. but as soon as i have my block and go into the select texture menu MCreator stops responding. sometimes it starts working again after 5 minutes but sometimes it takes so long i assume it chrashed so i just force quit the application.

Is that normal or is it a bug that can be fixed?

Big_guy9