Is this normal for them, or could there be a power problem in the house?

I also had to put a filter on the power for my subwoofer, but I think that is normal.

The sub has a hum, without the filter. The TV loses its connection to WiFi. (I know I should hardwire it, but it’s a temporary house.)

The dishwasher stopped once, mid-cycle. The other times, it just won’t turn on.

One of our TVs loses wifi occasionally also. I never figured out why. It's only a minor aggravation.

Had that problem with our dishwasher for about a month before it stopped working entirely. It would be dead so I would have to unplug it for 10 minutes or so and then plug it back in and it would come back to life. Finally just quit working entirely.

Our printer will disconnect from wifi and need to be reconnected. I don't think that's entirely unusual. Be prepared for dishwasher death.

As far as the TV, how far is your router from it? Could be a bad/weak connection.

I would go into the settings and update the TV

Then in the settings, go to your network connection and delete the current Wi-Fi connection, restart the TV then re-add it.

My Roku TV gives you a network test that shows you how good the connection is to the Wi-Fi, does yours do that? That could indicate the issue.

I found I could set my router to automatically reboot every night at 4 AM in its setup ware.
That cured all the rare but aggravating issues I had.