Strange behavior generated by Hardware (?)

I’m still a beginner in the area of development and there are a number of things that I don’t really know how it works, so maybe this is a silly question.

But when testing the project I prepared for the current GameJam, one of my friends who worked with me on the game started to suffer from a slowdown in the game (playing via Chrome) that affected the jump height and the scrolling animation of certain objects. On the same day, he tested the build in another browser (Brave) and the problem did not appear.

Bizarrely, after submitting the game to I tested the game on the site numerous times with no problems, but suddenly, the problem that plagued my teammate, started to affect me too: the jump decreased in size (and the game appears to be slower) causing softlock already on the second platform of the game.

I did some tests with this friend (who now has the game running normally), and a platform that I need at least gravity of 3769 to go up, he is managing to go up with gravity up to 4020. If the code is exactly the same in both cases, why the different behavior?

This also happens with object animation. The creatures in this test scenario have greatly altered movement.

Test without the bug:

Test with the bug:

It’s the exact same code and the exact same PC in both cases.

Recap how some skulls went through the tunnel in the first test and how when this bug is activating (the same one that is also limiting jumps) they don’t reach the lowest part of the scenario.

As the jump behavior in the game is connected to adjustments made by timer and variable tween, and the movement of the monsters, depends on a calculation of sin*SceneTime I was judging that it was a problem exclusively connected to calculations involving the passage of time, BUT, the test with the pure platform behavior, where jumping the same obstacle, it was possible only up to the gravity of 3769 and in another device it could even with gravity of 4020, seems to go the opposite way (unless the platform behavior works with timers too, under the hood)

This issue has me especially concerned, as I can’t seem to rely on gameplay fine-tuning, having to keep putting margin of error on things that should be accurate.

Has anyone experienced this, or could you imagine what might be happening?

Could it be that for unknown reasons, the game starts to run at a slower speed, and this not only delays the visuals but also significantly impacts the mathematical formulas of the game?