When a plug-in relies on the embedded Boost framework to support regular expressions, it can cause a crash because of unresolved dependencies.

The issue is that the 16.0 SDK uses Boost 1.65 and the 16.1 SDK uses Boost 1.72

Plug-ins compiled against the 16.0 SDK that use regular expressions will try to access an entry point __ZN5boost16re_detail_10650018get_default_syntaxEh (unmangled: boost::re_detail_106500) when handling regular expressions.

The problem is that this entrypoint's name is dependent on the Boost version (1.65).

This entry point is provided by the (on Mac) embedded framework

/Applications/Adobe InDesign 2021.app/Contents/Frameworks/boost_regex.framework/Versions/A/boost_regex

When a plug-in compiled against SDK 16.0 is used with InDesign 2021 16.1, this entry point does not exist any more.

Instead, the equivalent entry point is now boost::re_detail_107200 and boost::re_detail_106500 does not exist in InDesign 2021 16.1

That causes the plug-in to crash InDesign.

As a result, plug-ins that use boost_regex that are compiled for 2021 16.0 are incompatible with 2021 16.1 and vice-versa.