movement lag when sprint control is rebound to Shift

Since upgrading to 1.15.2 I'm seeing an intermittent delay in movement when sprinting forwards from standstill with custom sprint/sneak controls.

I've remapped the Shift key to sprint, and the ctrl key to sneak, as that is what I am familiar with from other games. This issue only happens for me when the sprint/sneak keys are swapped

I've recorded an example here, with the keys being pressed as an overlay, which shows first the delay, and then back to normal maps for sprint/sneak

The delay is not consistent, sometimes it's hardly noticeable, but seems most pronounced when I'm being attacked by mobs, and the delay at that point is most unwelcome

https://youtu.be/1PCgV98jMSw