As reported in the forum by user reckless, addr2lineui.exe shows an assert, "Vertical alignment flags are ignored in vertical sizers".
addr2lineui assertion triggered with wxwidgets 3.14
Vertical flags were generated by wsSmith, but this was corrected some time ago, so reopening the wxs with wxSmith is enough to get this fixed. There are more automatic changes, namely include sorting and Connect() parameters.
The attached patch contains the changes made by wxSmith.
Applied in SVN. Thank you!