It seems that bleeds are exported only when exporting all artboards at once. When exporting individual artboard to PDF, bleeds are not preserved.
Also I did not find a way how to enable/disable bleeds in Export persona > Slices settings. It exports always without bleeds.
Yes, these are a few new bugs with bleed. For some reasons the bleed export option has been moved from the presets and is now a separate option on the main export dialogue. Consequently no options to enable bleed is available in the export presets for the export persona. That should be fixed, i hope.
Thanks for letting us know! I've passed these on to development.
I’ve run into this problem too.