I can reproduce it with the default machine=svga_s3 setting in DOSBox, but not with the machine=ega setting, so the latter may indeed be necessary for the Windows 3.0 EGA driver.
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I can reproduce it with the default machine=svga_s3 setting in DOSBox, but not with the machine=ega setting, so the latter may indeed be necessary for the Windows 3.0 EGA driver.