Changing Engine Mode at Prelaunch Causes "Fake" Booster Cluster Startup

[SAMCG14]

Version: pre-release v3.0.0 Beta 3

It seems that if you change the Booster engine mode at prelaunch status and then you activate the engine using staging, the engine goes "on" but without a plume at all.

On the staging menu there's no sign of an active engine as there is no fuel bar, on the PAW there is a shutdown engine button but there is no thrust and the engine status is listed as off