This has been bugging me for a while but without a pattern for why and how it happened I couldn't really describe it in enough detail to pin-point. However, working in the 3D window pretty much constantly for the last few weeks and I've been able to understand what's happening:
It used to be that elements that were grouped and selected would
remain selected when they were un-grouped. For a while now that behaviour has been erratic: un-grouping a bunch of elements would result in only some of them remaining selected. Working in a plan view you don't get to see that this has happened, merrily carry on working with your un-grouped but selected (as far as you are aware elements), only to find that when you moved them, you only moved half of them in fact.
This is particularly frustrating with nested groups: un-grouping a parent group should break the enclosed elements back in to their constituent groups, and so on back until they're no longer grouped at all. I've been finding that this has been broken for a while: the first un-grouping command losing some elements from the selection such that subsequent commands are not carried out. OR: instead of breaking them back in to constituent groups it just un-groups a bunch of random elements.
Well, I've figured out that these elements are not random: this un-grouping deselection bug happens to any element which is identical to another element in the group but at a different vertical level. See screenshots attached: in the third image immediately after the second un-group command is issued you can see that all of the beams that automagically deselected themselves have a lower physical 'twin' who's element type and nodal points overlap.
Interesting that it doesn't distinguish between flat or slanted beams: the end nodes of all are overlapping at the same x, y point regardless of where their z points are.
Anyway. Long time no post. Long time bug bugging the hell outta me: hope it gets squashed in the next go-around...
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