Characters missing and menu not working

I am using LibreOffice 5.1 RC1 64bit English
Windows 10 64bit

There seem to be strange things happening.
When I look for files, the names do not show the Korean characters in the file names only the english. Explorer does not have any problem. This is in the recent documents list, or the startup page showing recent documents, but not in the file open browser window.
When I use the mouse to change the font of selected text, or to change the style, nothing happens. I have to use the keyboard.
When I use the down arrow to move the cursor to the next line in Writer, the cursor randomly (or maybe not randomly) jumps to an entirely different place on the line. This is not desired behaviour.

Are these bugs or have I done something wrong?
I am not a new user. I would call myself experienced rather than expert.
Thank you for any help you can give.

Has nobody any idea about these issues? Being unable to use a menu with a mouse is a big deal to me. Not seeing file names is a big deal to me.

I see this issue. Not sure if it existed in 5.0. I upgraded into 5.1RC from 4.x.
As RandomRabler37 notes, I can click on the small downward arrow for the dropdown and then select an option, but it does not get applied. E.g. I click on font dropdown and select a different font. But nothing happens. Another issue that I see is that I cannot drag on the scroll bar using the mouse. The dropdown disappears when clicked on scrollbar. I can scroll with mouse wheel, but can’t select.
Need a fix ASAP.

And to update on my previous post, I am on Windows Vista 64 bit. Have made sure that I am not using any mouse tweaks or mouse control software. Tested with different mice and on touchpad. Same behavior. Definitely odd behavior. Cannot comment on the other issue of random cursor placement/Unicode file names. Not seeing this issue as I am using English only.

OK, it’s more complicated. Sometimes the Korean characters do show up, such as one hour ago, but then they vanish again, like now.
The mouse problem is 100% all of the time. So is the cursor problem.