using D21 on a Pi4 do not work correctly

[mbonani]

We use a small strip of 40 leds RGB, we get several trouble wit colors specially with high brightness. We found a workaround using D18 pin that work perfectly. Analysing the signal there is a strange delay on the D21 pin:

there is 11 bits and then a small waiting time that as no sense

using D18 the whole bits are transmit in one shot :