I'm desperately trying to do some sound design and going nuts with the slow video engine and random acts. I have several tracks with clips and some of them have clip fxs. Opening a clip fx bin from another clip pops up the fx bin from a previous clip from the same track. WTF? Accidentally messed up some setting from a wrong clip. I can't reproduce this on a new project but happens on every track in the one I'm working with.
 

If you split a clip while it had an FX in it, all the subsequent splits will ilkewise have the same FX in them. 
 
The easiest way to speed up the video engine is to reduce the video file size. I convert any videos to compressed WMVs since they're only for reference (the audio ends up going into the video editing program).

Thanks Craig. Trying to minimize the video size could help indeed. I have captured the video with Xbox software (the one that Windows 10 has) from the game I'm working at. I have used this same method before with same video quality and don't remember having problems with the video engine. Just seems strange if something worked smoothly earlier and now doesn't.
 
I'll try to explain the other problem with images since it's a really strange phenomenon.
 
Here I have clips and I have selected the one highlighted in the picture:

Now when I press ALT + K (or open the clip fx bin with right click):

If you check the name you'll notice it's the fx bin for wrong clip.
 
My workaround at the moment is to insert fx:s from inspector.