I have a problem out of the X-Files.

I modified a countertop sub-assembly in a project. Later re-opened the project and found the subassembly had reverted to stock. I went in and (disappointedly) decided to start again. I inserted a machine token, hit save and redraw, and the subassembly reverted to the modified version. All was well. Went to make another change and it was back to stock. The previous machine token was still there. I inserted another token and hey presto! the modified version is back. This seems easily repeatable. Below are the two versions...

Anyone else seen this??