I think the error may be due to incorrect indentation. Don’t indent data beyond service. Align it with service like this:
action:
- service: switch.turn_off
data:
entity_id:
- switch.bathroom_tv
- switch.charlottes_bedroom_light
- switch.charlottes_tv_left
Not going to believe this … but i think this error was caused by a single dot that was missing from the original script and then the revised automation
Old entry
switch_master_bedroom_tv_b
New Entry
switch.master_bedroom_tv_b
Will do some testing and see if that single character caused all these problems
Haha! Good work!
Yes, now that I look at it more closely, I even have it listed in my own post because I just copy/pasted what you shared (without closely examining each entity).
switch_master_bedroom_tv_b is not a valid entity reference and will cause a problem.
Ah I didn’t know that. Thanks for letting me know. 
I’m so used to the second notation, because to me it is clearer this way.
The devil always lies in the details 
Glad you were able to solve your issue.