No idea if it matters, the 3rd bar has font-4 = "JetBrainsMono Nerd Font Mono:style=Regular" and the 4th does not. Maybe the missing icons are from the nerd font and those on the 1st and 2nd bars are from the font awesome?
It would also help to know if and what errors are displayed running polybar from terminal, or in the log, is there anything like Dropping unmatched character?
I’m not using polybar though, just thinking out loud.
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