It may not have anything to do with 'Insert inside' as I've found out when ungrouping the items and noticing the 'opacity' reverted back to how I'd set it (and could see the % number shown) previously when grouped (with coloured fill).
...It seems to happen when inserting shape with 'Insert inside' grouping shapes, then changing colour and reapplying opacity works. I've found that making a shape with one colour, ing or duplicating these shapes then grouping shapes, opacity applies but reverts back to 100% ...changing said colour to grouped shapes and reapplying opacity work, without opacity reverting back to It's default 100%. It's still an issue and I thought It was worth mentioning as no one else had brought it up? Regards, Euro