i am also using ubox with a 2 gb bandwidth. Sometime and some channel do lag. it is also true that in the night the lag increases and also weekend.
In a share network and there are many user esp playing game which require lots of download and upload data will slow the speed down thus made the viewing unpleasant.
Further, another reason is the ubox is serving many users concurrently thus limiting the data speed. to test out what u could do is installed a simple iptv and get a lightweight and fast
playlist to try it out if the ubox is slow or your system cannot handle.

Goodluck hope you can find a solution.