unwanted layer merging in Illustrator

[Lunar Graphix]

Sometimes when we receive PDF and EPS files, all the layers have been merged together.

For example:
Computer 1 creates a file with 4 layers (Print, reg marks, thru-cut, crease)
Computer 2 opens file and all layers have been merged onto 1 single layer. In fact the other layers don't even exist anymore. Also everything in the merged layer has a clipping mask over it?
Yet when computer 1 opens the file again all the layers are still there.

Same versions of illustrator on computers 1 & 2.

Has anyone had this issue before? What was your fix?

 

[Saturn]

Was going to say this happens when you open a newer .ai file in an older version, but sounds like your versions are exact. There's also a "preserve illustrator editability" check box if saving as PDF. Than may have gotten unchecked?

 

[Lunar Graphix]

Was going to say this happens when you open a newer .ai file in an older version, but sounds like your versions are exact. There's also a "preserve illustrator editability" check box if saving as PDF. Than may have gotten unchecked?

Thank you for the reply.

Yep versions was the first thing I checked after googling. We have a ton of creative cloud licensees and all of our office computers are set to update the suite automatically.

Preserve illustrator editability is still checked.

Also tried saving as legacy but that didn't help either.

Even stranger, the problem doesn't happen in reverse..

situation 1
comp 1 saves file with all layers visible
comp 2 opens and layers have been magically merged
situation 2
comp 2 saves file with all layers visible
comp 1 opens file and layers remain in tact

I've gone as far as to format the entire PC and the issue persists.

 

[Bobby H]

Just a spit-balling guess, but are there any unique plugins in use on the computer used to create the artwork and generate the PDF? That's really the only other factor I can think of which could possibly cause a layer structure to collapse in an Illustrator-generated PDF or EPS file opened on another computer. In the case of PDF files the Adobe police would tell anyone PDF is not a editable format; it's for display and print only. If preserving layer structure is really important I would recommend trading .AI files rather than PDF or EPS, especially if everyone in the production chain is using current editions of Adobe Illustrator CC. Make the last computer touching the .AI file generate a PDF for print on that end.

 

[Boudica]

If you save the file as an illustrator pdf it should keep the layers intact.

 

[Solventinkjet]

If you save the file as an illustrator pdf it should keep the layers intact.

Just make sure to check the, "Preserve Illustrator Editing Capabilities" box.