By setting sortBy for each group the last wins. See https://github.com/TYPO3-Solr/ext-solrfluidgrouping/blob/0b1e166110f2455f7536dacf8c5b56ca32904a80/Configuration/TypoScript/setup.txt#L14 we should throw an exception by setting sortBy inside the group block. And move sortBy one level above.
By setting sortBy for each group the last wins.
See
ext-solrfluidgrouping/Configuration/TypoScript/setup.txt
Line 14 in 0b1e166
we should throw an exception by setting sortBy inside the group block. And move sortBy one level above.