I am also having the same issue as others with excessive CPU usage causing the TOS page to be nearly unusable.
I installed TOS 5 the other day, using the 5.0.135 initialization installer. Everything was going fine, until I restarted my NAS and then it seems like it decided to index all the thumbnails (I have 11TB of pictures and videos). Now my TOS page is basically lagged out and I cant access the 'desktop' part of TOS unless I wait a LONG time ( 30+ minutes), when i did that, it said the ThumbnailDaemon was using most of my CPU. I did not enable and never have enabled media indexing and no applications are installed.
https://imgur.com/a/ZdGjVkA
As you can see in the image my NAS has been at 100% usage for 17+ hours since the first restart that caused this.