ALL Self Levelling Compounds, Thinsets, and Grouts have an absolute shelf life and they do in fact expire. Just because that product was still technically within the limits that doesn't mean it hadn't already gone bad. It all depends on how the products are handled as they move through the marketing chain.
Just a few weeks ago I also had an issue with some Custom Level Quick. In this case the product went to hell upon installation. There was no expiration or manufacturers code on the bags I bought so I couldn't determine how old the product really was. I called Custom and when I described the problem the techie first told me it sounded like an installer error.
Well.......I set his ass straight in a heartbeat and he then nice-up and offered to immediately replace the product I needed at no charge. When I explained what it was doing he then said he recognized those issues as "out-of-date" product. That's fine and I appreciate that part but WHAT THE HELL WAS I SUPPOSED TO DO WITH THE CRAP I HAD ALREADY INSTALLED. Who's gonna take that out and redo it?
What makes then think all installers are idiots?
I think we all should hammer all the manufacturers at every opportunity to make them print life cycle information on all of their products that have the ability to expire on the shelf. I don't mean secret hidden codes, I mean plain English up-front dates and warning statements for all to readily see and use.
It's a pisser for sure!