plotting – Plotmarkers not being displayed correctly

When I export the following Plot to a PDF, the Plotmarkers appear jagged and don’t look like they should.

Legended(Show(
  Plot(ShannonEntropyAnalytical(x), {x, -10, 0.5}, 
   PlotStyle -> Directive(Thickness -> 0.007)), 
  ListPlot(ShannonEntropyOrder0, PlotStyle -> Black, 
   PlotMarkers -> {Graphics({Black, Line({{-1, 0}, {1, 0}}), 
       Line({{0, -1}, {0, 1}})}), 8}), 
  ListPlot(ShannonEntropyOrder1, PlotStyle -> Orange, 
   PlotMarkers -> {{(FilledCircle)}, Scaled(0.01)}), 
  ListPlot(ShannonEntropyOrder2, PlotStyle -> Blue, 
   PlotMarkers -> {Graphics(Rectangle(), ImageSize -> 6)}), 
  ListPlot(ShannonEntropyOrder3, PlotStyle -> Red, 
   PlotMarkers -> {Graphics(Rotate(Rectangle(), 45 Degree), 
      ImageSize -> 7)}), Frame -> True, 
  FrameLabel -> {{MaTeX(
      "\boldsymbol{\text{\textbf{S}}_N(\Lambda)}", 
      FontSize -> 20), 
     ""}, {MaTeX("\boldsymbol{\Lambda}", FontSize -> 20), None}}, 
  LabelStyle -> {Black, Bold, Medium}, 
  FrameTicksStyle -> Directive(Italic, FontSize -> 15), 
  ImageSize -> 500, 
  FrameStyle -> Directive(Black, Thickness -> 0.003)), 
 Framed(Column({LineLegend({Directive(ColorData(97, "ColorList")((1)),
        Thickness -> 0.12)}, {Style(
       MaTeX("\textbf{Analytical Values}", FontSize -> 16))}), 
    PointLegend({Red}, {Style(
       MaTeX("\textbf{Numerical Values 3rd order}", 
        FontSize -> 16))}, LegendMarkers -> {(FilledDiamond), 18}), 
    PointLegend({Blue}, {Style(
       MaTeX("\textbf{Numerical Values 2nd order}", 
        FontSize -> 16))}, LegendMarkers -> {(FilledSquare), 18}), 
    SwatchLegend({Orange}, {Style(
       MaTeX(",\textbf{Numerical Values 1st order}", 
        FontSize -> 16))}, LegendMarkers -> {(FilledCircle), 17}), 
    PointLegend({Black}, {Style(
       MaTeX("\textbf{Numerical Values 0th order}", 
        FontSize -> 16))}, 
     LegendMarkers -> {Graphics(PolygonMarker("Cross", 100))})}), 
  RoundingRadius -> 5))

This is how they look for instance:
enter image description here

and my Export code looks like:

Export("ShannonEntropyPlot.pdf", ShannonEntropyPlot)

Any advice on how to fix this? I am using Mathematica 12.3.