we zipped up 10 cad files, sent the zip file to someone. they added info to the zip file without unzipping it. another person unzips that zip file and all of the cad info shifted 1 file up. IE. Drawing 3 linework is showing up in Drawing 2 and drawing 2 linework is showing up in drawing 1.

has anyone ever seen anything like this?

we think it is the adding of info to the zip while it was still zipped but seams crazy. looking for anyone that has seen the same