Flicker problem with A7sII at 25 frames, shutter 1/60

[KarineA]

I'm french and I did a recent shooting in the USA. I had a huge problem of flicker on a lot of lights. I shoot in 25 frames per seconds, and my shutter was 1/60, which should prevent me from flickering. I had an other camera, an FS7 who showed no flicker with the same settings. So the shutter 1/60 isn't a true 1/60. So for all shooters from the PAL world, it's a huge problem. I had the last firmware update (v3).