It sounds as if something changed to 60Hz playback. No, I can't offer a direct setting to look at but
60 / 50 = 1.2 speed so you can bet something is set to 60 Hz.
With many smart TVs I've run into folk installing the wrong firmware, trying to get the unit to lie about its region so eventually you see this. The cure is never the same so I can't be specific.
I'm having an odd problem watching DVD's and Blu-ray's that I've ran out of ideas trying to fix, so I'm hoping if I just give all the information I can someone will have had the same problem before and know how to help.
I was watching a DVD on my PS3 2 days ago, connected via HDMI to my panasonic tx-l42eb LCD TV, it was running fine until I rewound a bit, and I don't know if I accidentally pressed a button or something, but suddenly it was playing slightly faster, like 1.1x speed. It has continued to do this with every DVD and Blu-Ray I've tried to watch since then. I tried using different Blu-Ray player with the TV and it did the same thing, so I think it's a TV problem. I've reset the TV to factory settings and tried different HDMI cables and nothing has helped. I'm in the UK so everything is PAL, incase that changes anything.