luaotfload always being invoked

Every time I run lualatex, luaotfload-tool is being invoked. As a trivial example,

documentclass{ltjsarticle}
usepackage{luatexja} % ltjclasses, ltjsclasses を使うときはこの行不要
begin{document}
section{はじめてのLuaTeX-ja}
ちゃんと日本語が出るかな？
subsection{出たかな？}
長い文章を入力するとちゃんと右端のところで折り返されるかな？
大丈夫そうな気がするけど．ちょっと不安だけど何事も挑戦だよね．
end{document}

This file is ‘junk.lua’:

$ make junk.pdf
lualatex < junk.lua && mv texput.pdf junk.pdf
This is LuaHBTeX, Version 1.12.0 (TeX Live 2020) 
 restricted system commands enabled.
**LaTeX2e <2020-02-02> patch level 5

L3 programming layer <2020-08-07>
*(/opt/texlive/texmf-dist/tex/luatex/luatexja/ltjsarticle.cls
Document Class: ltjsarticle 2020/05/30 ltjsclasses 
(/opt/texlive/texmf-dist/tex/luatex/luatexja/luatexja.sty
    . . .
(/opt/texlive/texmf-dist/tex/luatex/luatexja/patches/lltjfont.sty
(/opt/texlive/texmf-dist/tex/latex/base/tuenc.def)
(/opt/texlive/texmf-dist/tex/latex/ms/everysel.sty)
ABD: EverySelectfont initializing macros)
(/opt/texlive/texmf-dist/tex/luatex/luatexja/patches/lltjdefs.sty
luaotfload | db : Font names database not found, generating new one.
luaotfload | db : This can take several minutes; please be patient.

‘luaotfload-tool’ with diagnostic output shows all the ‘fontloader-*.lua’
files have checksum errors, but I have no idea if this is relevant. I read
in another post that luaotfload can do this if the font name is wrong, but
this is vanilla luatex (well, luatexja) so I can’t see why that would be a
problem.

Any suggestions would be most welcome.

P.S.

Running ‘luaotfload-tool -v -vvv -u’ (command copied from elsewhere) I get a massive amount of output, but output at the end may be significant:

luaotfload | db : Found 4377 font files; 0 new, 0 stale entries.
luaotfload | db : Creating filename map.
luaotfload | db : Conflicting basename: "ASANA" already indexed in category texmf, ignoring.
luaotfload | db : Conflicting barename: "ASANA" already indexed in category texmf/ttc, ignoring.
luaotfload | db : Analyzing families.
luaotfload | db : Analyzing shapes, weights, and styles.
luaotfload | db : Ordering design sizes.
luaotfload | db : Collecting fontnames.
luaotfload | db : Rebuilt in 29611 ms.
luaotfload | db : No new or removed fonts, skip saving to disk.
luaotfload | cache : Lookup cache saved.
luaotfload | cache : Lookup cache emptied.
luaotfload | db : Fonts in the database: 2162

‘Not saving to disk’? ‘Lookup cache’ ‘saved’ then ’emptied’?

P.P.S I am starting to get a bad feeling about lua; it appears to be rather shoddy:

$ luaotfload-tool --find "Libertinus Serif"
...texmf-dist/tex/luatex/luaotfload/luaotfload-features.lua:432: attempt to index a nil value (field 'normal')

I ran this on Solaris and Linux with the same result.

UPDATE:

$ uname -a
SunOS euros 5.11 11.4.0.15.0 i86pc i386 i86pc
$ luaotfload-tool -D -u    
luaotfload | db : Font names database not found, generating new one.
luaotfload | db : This can take several minutes; please be patient.
$ luaotfload-tool -u
luaotfload | db : Font names database not found, generating new one.
luaotfload | db : This can take several minutes; please be patient.
$ luaotfload-tool -D -u 
luaotfload | db : Font names database not found, generating new one.
luaotfload | db : This can take several minutes; please be patient.

whereas,

Linux zephyr 4.1.12-124.30.1.el7uek.x86_64 #2 SMP Thu Aug 8 01:38:50 GMT 2019 x86_64 x86_64 x86_64 GNU/Linux
$ luaotfload-tool -D -u     
$ luaotfload-tool -u
$ 

That is, on my linux machine the ‘database’ files are built so running with ‘-u’ does nothing except scan files presumably. In contrast, on Solaris it always complains about ‘Font names database’ not being found which suggests some file(s) is or are not being written, or are perhaps written but null.