I use an appletv. I have the version with a Ethernet port. It plays everything I’ve thrown at it so far and don’t have to endure commercials. The downside is you have to create an Apple account to install apps on it and not all apps are available. It’s also expensive.

Try using pcpartpicker.com. You can do your build on the site and it will list the best deals for the components you choose. As a bonus it will check to see if there are some glaring incompatibilities at the same time.

All drives will ultimately fail, could be 10years, could be 10mins. If you don’t want to lose your data, back it up. Have a storage drive and a backup drive. Don’t both connected them to the router. Use an alternative method to connect , like to a computer and have run a backup protocol on a regular basis. As for 2.5 over 3.5, the 3.5 are usually faster but it probably doesn’t matter reliability wise.

I would second the bad disk. I thought bad permission but since since it seems intermittent, the bad disk is the better guess. It would be good to get more info like what’s it running on, is it an array, etc.