I tried on SpecEmu ( Latest Version Update v3.2 Buld 25/10/18 see here: https://www.worldofspectrum.org/forums/ … ent_948741 )
and Chicagos30.tap / CHICAGO.TAP from http://www.worldofspectrum.org/infoseek … loadpics=1
on emulated Spectrum 128k with esxDOS UNLOCKED 128k / v0.8.6-DivIDE 32k and with "New NMI.SYS" v0.0.16
( New NMI.SYS: http://board.esxdos.org/viewtopic.php?pid=1012#p1012 )
and have most times NO problems with sending a NMI and e.g. save the game to a snapshot.
(On first try this may also reset the spectrum, but after loading in the .TAP and starting the game, next time NMI.SYS works. I also testet yet in esxDOS included "Old NMI.SYS" and this seems to be a litlle less stable than the "New NMI.SYS").

Is it nmi.sys thing or is that determiner programs do not support the interrupt function?

I have tried this behavior in emulator and I get the same results as in real machine

Merry Christmas