Been messing around with walls today and yesterday, haven't had any issues. Which walls exactly are giving you problems? "Pioneer Log Wall ...", "Mason Granite Wall"?

Also, when you say placed, is it when you create and/or move the ghost, or when you actually add the materials and build the wall?

How are you measuring memory leaks?

Or are you simply experiencing lower / fluctuating frame rate and ping when placing building parts? In this case, this is normal and depends on your system. Placing building parts requires a lot of client side calculations. Depending on the amount of nearby construction that gets checked and your system specifications these calculations can certainly cause frame rate (and in turn ping, which measures actual ping + delays due to low frame rate) to fluctuate.

I'm closing this one for lack of response and testing not showing any memory leaks. I believe this is just slowed frame rate due to calculations during construction.