I'm just going by what Earl told me over the phone.
The first indication that Earl had of this problem was a repair that was needed by a police officer on his .40 P99. Earl was going to replace the barrel, and the replacement would not fit into the slide. The slide was out of spec in relation to the barrel made by Walther. Walther is not known for their shoddy machining tolerances. If this slide had been made by Walther, the barrel should have dropped right in.
After checking out the slide further, he found it was made of SS and obviously made by S&W. He can still import the .40S&W, but he does so only with the LE mags, and he does not import these regularly.