Plasticizer Migration

This isn't much to go on.

Is the rubber foam or solid. How thick? How hot is it in the room? Are the stains at the joints?

What's under the rubber?

How soft compared to new?

"One guy told me" Was this guy connected with the MFG?/Seller? or was he next to you in a bar?

Did any of the stuff feel greasy when handled?

It's plasticizer.

It is the recycled rubber from tires like in fitness rooms, 10mm thick or a bit over 3/8 inch, the stains are mostly at the joints but I swear the whole floor looks like it is fading, the guy wasn't the manufacturer but a different installer, he probably does drink, so do I a bit,....but no known reason for him to BS me...

I have researched this, but the answer is not obvious. To me it looks like the "plasticizer" in the vinyl is reacting not with the rubber but with the urethane adhesive. I just don't have the inorganic chemistry background to figure out what is the reaction exactly. I love the feel of the underlayment, way better than foam like for a carpet, and I have had some of the same stuuf out in my horse barn for years before they started selling it in a similar form as underlayment

Your first post said you used acrylic adhesive, this time it's urethane. I don't think it matters.

I think it's those used tires you've got under your luxury tile. If you think about it, the stuff you walk on is much softer than the stuff your car rides on.

It gets that way through the addition of lots of stuff, including plasticizers. With the layer of "glue" and an over layer of luxury tile, you've sealed the bad things in. It gets out by oozing through the joints in your tile.

Take the rubber underlayment out to the barn.