I found out that there is an upper limit to the number of live folders one can have in their startscreen. On my HTC one M8 that limit is 27 sharp.
If I have 27 folders everything is OK, but when I add one more I get that "loading..." for a couple of seconds every time I hit the Windows button.
Add some more and you get it for longer time and when you scroll through the startscreen too.
And if you continue adding folders, you eventually come to a point when the "loading.." lasts forever and you can do nothing else than hard resetting (you get it even after a restart).
How can I avoid performance degradation when creating a lot of Live Folders?