Some computers are faster than others. Some are so fast that an action can actually be called by the program before the previous action has had a chance to finish and register.
To insure that the routines are processed in the proper 'order,' a short (very short) pause needs to be inserted by the program to slow things down just a bit. That pause is invoked with a simple switch. You set it only once, and forget about it after that.
To turn the Apply Wait feature to ON, click the Utilities/Settings entry from the Pathagoras drop down menu. On the Miscellaneous Settings tab, check the 'Allow time to process actions' button.
Don't be too concerned about the 'slow down.' It is less than one-tenth of a second and simply is not a noticeable pause. (Actually, the delay is so insignificant that it doesn't hurt to have this feature set to ON even when you have not experienced processing issues such as those above.)