On my side 1.16.27 is pretty stable.
The Heavy Fighter 'issues' are no bugs, as Sirius said, those are part of the design to make it 'Heavy' (more Shields, Energy, etc.)
And yeah, 200 is usually the max shields for the Standard ship on all Descent versions, and on D2X-XL, I think the Heavy one supports up to 220 and the Light one just up to 180.
The Music bug you said, may be related to some general Sound issues. Make sure you have the Hi-res sound pack installed for D2X-XL and that the d2x.ini file has the -midifix 1 line, that usually fixes most of the sound/music issues.
EDIT: After seeing another post of you here on the DBB, I would say Krom is right. Never mix D2X-XL and Rebirth on the same installation folder. Make different installation folders for each port, and you will have much less issues for sure.
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