MPC doesn't regain focus if on top

Steps to reproduce:
1. Open MPC window with option on top
2. Switch to other window while having MPC on top
3. Close the other window

Expected behaviour:
MPC regains focus

Actual behaviour:
Another background window or desktop gets focus and MPC window is unactive (gray color)

It regains focus normally if it's not on top though.

I use Win8.1 now, but it's the same in other versions as well.
It was always in any K-Lite Codec Pack version. Now using MPC-HC (Nightly 64-bit) 1.8.8.22.

It is Windows who decides which window gets focus after closing a window. It seems to be in order of last having focus.

Last having focus was MPC and it's not getting back the focus, but only if it's on top, if it's not on top it regains focus normally.
If it Windows who decides then maybe it's being lied which window had the last focus?
My guess is that there is a bug with the 'on top' function.

Here it works correctly with on top enabled. Open windows gain focus in correct order when closing. Tested on both Windows 7 and 10.

It can't be a bug in the on top function, because on top works fine, and how that works is completely unrelated to regaining focus.

Then what is the problem?

Some other application on your computer may be messing with the focus. Or it is just Windows being buggy.