50Hz vs 49Hz - Vintage Polish Computer Terminal

[MightyFrame]

So, I went to Poland last fall and brought home this beautiful computer terminal, possibly the first one ever in the USA.

Of course it's designed to run on 220v 50Hz, no surprise, and we have 120v 60Hz here in the USA. We can easily get 240v of course, but it's still 60Hz.



Now, knowing this, I bought a 12v to 220v 50Hz inverter that is supposed to support European "appliances".

But when I try to power up this terminal with it, this happens:

https://www.youtube.com/watch?v=0f1xM0PDezc

Is this obviously the 49Hz vs 50Hz that I originally noticed, or could this be something else?

Appreciate your opinions here, always.

Best,
AJ