Test in Manufacturing:

10.4.6
Dual 2.7 GHz
4.01_M38
Three showed the same bug

Test in RTS with reworked rentals

10.4.5
Dual 2GHz
4.01_m38
3 tested positive for the bug

I have noticed one more thing. If I only click the time code edit box, and not press enter but click on the next box to edit, it ALWAYS leaves the boxes open after closing the window. So if you close the edit boxes properly by pressing enter and not click on them after editing them, you shouldnt see the problem.