Maximum acceleration for a given velocity in movel

I’m trying to use movel on a UR3 for a small movement of about 10mm, at low velocity (between 2 and 10 mm/s). I want to have the highest possible acceleration to reach the target velocity as fast as possible. While doing some testing, I’ve noticed that accelerations relatively large compared to the speed can’t be reached ; in fact, it seems that the robot takes at least about 0.35 seconds to reach its targeted speed. If the acceleration is too great, the velocity curve during the acceleration phase is flatter than required, and consists of two different slopes.
Here is an example for a speed of 10mm/s and an acceleration of 100mm/s2, for a movel along the X axis:

If I multiply by 10, i.e. for a speed of 100mm/s and an acceleration of 1000mm/s2, I get the same result scaled by a factor 10. For me, the issue is therefore not linked to the safety limits for the speed and acceleration but to a relation between the two given values.

I’ve checked the joint positions, speed and acceleration and I’m far from any limit, I also made sure I wasn’t in a singularity.
The deceleration phase isn’t affected by this issue, it is always at the targeted acceleration.

My assumption is that this is a safety limit on the robot to avoid high accelerations relative to the speed: is that correct ? In that case what’s the precise limit and is there any way to go over it ?