That is strange.. the only way the error could continue to happening is if $gameActors.actor(1) was undefined or null. Meaning that no actor with ID 1 exist.
But you said it work fine with $gameActors.actor(1).name()
So, can you upload to me a sample project replicating the issue, so I can investigate? You can either upload it somewhere and send me the link here or send me the link through discord: hakuenstudio