The only way to solve this is to have someone test from the current GTK version backwards to find one which works as expected (obviously jumping back a number of releases is acceptable to try and narrow things down quicker). However, I don't know that any developers have the time, motivation, or ability to do this. While I don't like the regression, I don't consider it a blocker compared to the security issue we're looking to get patched with newer GTK libs.
The only way to solve this is to have someone test from the current GTK version backwards to find one which works as expected (obviously jumping back a number of releases is acceptable to try and narrow things down quicker). However, I don't know that any developers have the time, motivation, or ability to do this. While I don't like the regression, I don't consider it a blocker compared to the security issue we're looking to get patched with newer GTK libs.