Different brightness levels of a rating component generated by the same custom code

I am using the same rating component in two different routines of my expt. Its custom code is:

scale=None,
pos=(0,-0.85),
low=1, high=4, precision=1, labels=('Guess', 'Sure!'),
tickHeight=1.7,
markerColor ='White',
markerExpansion=1,
lineColor='Black',
showValue=False,
markerStart=-8,
noMouse=True,
respKeys=responseKeys_conf,
acceptPreText=' ', 
acceptText=' ',
marker='glow',
maxTime=confWindow,

Despite the code being the same, the brightness level of the blob that appears on top of the tickmarks as a key is pressed, is different between when the first rating component is used and when the second one is (in a later trial in the experiment).

It seems to me even though the parameters in the custom code appear to be absolute, they are in fact relative to some hidden variable, which probably changes between the time when the first rating appears and when the second rating appears.

PsychoPy version (e.g. 1.84.x): 3.2.4