There was some TV makers that broke video playback at just over 2 hours on purpose to stifle video piracy. This sounds like your smart TV has this video playback limited to 30 minutes. That discussion is on the web so I won't write at length about it.

My fix was to not use the Smart TV apps and player but use anything else. Today I use an Intel NUC for playback. There are other devices that can do this too (your PC for example.)