Hi David,
if I understand correctly you see a problem with the
Merge_rests_engraver (your attached file from-NR.ly)?
That engraver didn’t merge MultiMeasureRests until 2.19.65 and does so
since 2.19.80 (the first prerelease for 2.20.0, hence the version number
jump from 65 to 80). However,
There seems to be a problem in the merging whole measure rests
code. With 2.18.2, I'd been using the 336-based snippet from
https://raw.githubusercontent.com/wbsoft/lilymusic/master/include/merge-rests.ily
for some years, though I changed 0) on the 110th line to 1)
in order to get
