I get stair-stepping/jagged line when using High Speed Record in X-T4 is this normal?

Hi! Recently I bought an XT4. I know that this camera doesn't have an anti aliasing filter.
and I get this result when shooting slowmo (high speed record). Is this normal?

My setting was correct I guess?

24p 120fps High speed record setting with 240ss, HD and H-265 in body record.

I've tried to change other setting just for the sake of trying to produce different result, like turning off focus peaking, using different color profile, using different file format, but nothing's changed.
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update1 : tried to compare with the 120fps from sony rx100vi, the result is smooth..
update2 : tried to compare with the other leg... the only one jagged is the left one...

update1 :

update 2 : left leg vs right leg

120fps sony rx100vi

Fuji Maine wrote:

What you are seeing is moire artifacts. The 240fps is pretty much a gimmick and will look like that in most scenes. It's a two fold issue, first is that even though the output is in 1080 it's actually capturing in 720p which is why it looks soft. The other issue is that even taking in the info at 720, 240fps is taking in a ton of "information" and the processor isn't capable of a high enough bit rate to actually process the information so you get artifacting like in your example. The 120fps looks good though so I'd have l just stick with that. If you shoot above 180 degree shutter you can also get away with further slowing the 120fps in post with good results.

The screenshots above is the result of 120fps. I didn't use the 240fps at all. That's why i'm confuse about this. The 240fps is worst than these results .
What I mean by 240ss is the shutter speed setting.

cineplorer wrote:

Fuji Maine wrote:

What you are seeing is moire artifacts. The 240fps is pretty much a gimmick and will look like that in most scenes. It's a two fold issue, first is that even though the output is in 1080 it's actually capturing in 720p which is why it looks soft. The other issue is that even taking in the info at 720, 240fps is taking in a ton of "information" and the processor isn't capable of a high enough bit rate to actually process the information so you get artifacting like in your example. The 120fps looks good though so I'd have l just stick with that. If you shoot above 180 degree shutter you can also get away with further slowing the 120fps in post with good results.

The screenshots above is the result of 120fps. I didn't use the 240fps at all. That's why i'm confuse about this. The 240fps is worst than these results .
What I mean by 240ss is the shutter speed setting.

The artifacts you’re seeing might be from line skipping, which the camera may need to do in order to process the data fast enough to achieve those high frame rates.

Wezre wrote:

cineplorer wrote:

Fuji Maine wrote:

What you are seeing is moire artifacts. The 240fps is pretty much a gimmick and will look like that in most scenes. It's a two fold issue, first is that even though the output is in 1080 it's actually capturing in 720p which is why it looks soft. The other issue is that even taking in the info at 720, 240fps is taking in a ton of "information" and the processor isn't capable of a high enough bit rate to actually process the information so you get artifacting like in your example. The 120fps looks good though so I'd have l just stick with that. If you shoot above 180 degree shutter you can also get away with further slowing the 120fps in post with good results.

The screenshots above is the result of 120fps. I didn't use the 240fps at all. That's why i'm confuse about this. The 240fps is worst than these results .
What I mean by 240ss is the shutter speed setting.

The artifacts you’re seeing might be from line skipping, which the camera may need to do in order to process the data fast enough to achieve those high frame rates.

I did a lot of tests about this and I think you're right.
Accidentally my first try is using gunpla that has just right condition (light etc) to produce the line skipping.
I tried with another scenario and scene , didn't find any jagged line.
this  might be a normal thing for XT4.... 🤔