These lines determine whether bf:duration is generated or not. This is detected by finding the character '|||' or 'nnn' from character 19 on wards in tag 008. Should three spaces be handled the same way? Than add an extra line:
<xsl:when test="substring($dataElements,1,3) = ' '"/>
https://github.com/lcnetdev/marc2bibframe2/blob/a2c5a96e0286c45bfd441bd493d31a0f5b86904a/xsl/ConvSpec-006%2C008.xsl#L497
These lines determine whether bf:duration is generated or not. This is detected by finding the character '|||' or 'nnn' from character 19 on wards in tag 008. Should three spaces be handled the same way? Than add an extra line:
<xsl:when test="substring($dataElements,1,3) = ' '"/>