It seems to be mingw. So I would try to recompile dll with or without debug…
Edit: Now I found something which could (maybe) help. But maybe it is just junk info.
GNU C99 5.4.0 -m64 -mtune=generic -march=x86-64 -ggdb -O2 -std=gnu99 -fdebug-prefix-map=/cygdrive/i/szsz/tmpp/cygwin64/mingw64-x86_64/mingw64-x86_64-runtime-5.0.2-1.noarch/build=/usr/src/debug/mingw64-x86_64-runtime-5.0.2-1 -fdebug-prefix-map=/cygdrive/i/szsz/tmpp/cygwin64/mingw64-x86_64/mingw64-x86_64-runtime-5.0.2-1.noarch/src/mingw-w64/mingw-w64-crt=/usr/src/debug/mingw64-x86_64-runtime-5.0.2-1
I would try to use same options.
-ggdb (for debug) is probably good start to add first! 