Too many "undo's" causes layout to change?

I'm wondering if anyone else experiences this: if I do too many Control + Z's in a row to undo text changes, my page layout changes. I haven't determined the magic number when this happens, but I've sadly had it happen more than once and I saved my file before realizing it. So lots of rework to fix my layout. (In particular it changes from a two-column layout to three columns. Even the Master Page changes.) Importing formats from other files sometimes fixes it, sometimes not. I'm just wondering if this is a bug? Thanks.