I got this game some time ago to run it on an old machine and it worked well.
Recently I redownloaded it and now it has significant slow downs at random for some reason.
Not sure if the dosbox got updated or something but changing the output from opengl to texturenb seems to have fixed the slowdowns.
However, there still seems to be some lag spikes, indicated by the music cutting off occasionally.

Edit: It also randomly crashes between phases now and judging by the patch notes, it seems like the dosbox version is what broke it.