The cleanIcons command is using oslllo/svg-fixer behind the scenes. Unfortunatly the cleanup is mediocre, because multiple paths are not merged, but only the first path in SVG is kept, every other path is deleted.
You can reproduce the behaviour here:
https://iconly.io/tools/svg-convert-stroke-to-fill
This leads to hard to identify problems and therefore cleanup harms more than it helps. Either remove the command or replace the tool behind with one which does a proper merge first.
Btw: Using this SVG in a font without cleanup works
The cleanIcons command is using oslllo/svg-fixer behind the scenes. Unfortunatly the cleanup is mediocre, because multiple paths are not merged, but only the first path in SVG is kept, every other path is deleted.
You can reproduce the behaviour here:
https://iconly.io/tools/svg-convert-stroke-to-fill
This leads to hard to identify problems and therefore cleanup harms more than it helps. Either remove the command or replace the tool behind with one which does a proper merge first.
Btw: Using this SVG in a font without cleanup works