When using a grouped column any columns using a flex attribute within it are not 'flexed' to the available width.
See:
https://fiddle.sencha.com/#fiddle/t3k
When using a grouped column any columns using a flex attribute within it are not 'flexed' to the available width.
See:
https://fiddle.sencha.com/#fiddle/t3k
Thanks for the report. Looks like this is a known issue being tracked as EXTJS-11525. Still unresolved at this time.