Hi @abs - sorry for the “lost instance” issue. Good to see you again - hope you are well.
Let’s name this issue: MIBR (missing instantiation before reload)
Are you affiliated-with @DANIEL_S and his near-identical-sounding issue? (Also HERE.)
Wingy curious IF/NOT you are working on SAME project, or if IDENTICAL ISSUE (MIBR) on separate projects.
Both you and @DANIEL_S claim issue happens intermittently (sometimes) and claim “reload browser, problem fixes”, yes? nod.
@DANIEL_S included some code in his first report. Same/Near-same code for you, ABS?
Let’s talk cross-browser and cross-platforms, now. Can you (both) test with different browsers, different OS, and different versions of BJS/other-used-libs?
Lastly, IF you are both creating (master) mesh first, and LATER using JSON to create instance… IS another SPECIFIC instantiation of SOME MESH… performed just BEFORE or AFTER the missing instance?
In other words, could an instance made BEFORE or AFTER the MIBR… be causing the problem, and problem is difficult to locate BECAUSE too much looking at MIBR and not enough investigation of pre-mibr or post-mibr actions? Does instance before mibr… or after mibr… actually cause problems (bad instantiation pre-state or post-state)?
Can you “shuffle” the ORDER of the instantiations? Is the MIBR always the 3rd instance of a group of instantiations? Can you de/re-group/sequence… and then re-check symptoms? (& similar tests)
Does the MIBR always happen to the same “master” mesh? Still… only sometimes?
So many questions, huh? nod.
Yeah… good idea (hi aW!). AND setting them… from command line, ideally.
Sorry for butting-in… Wingy not really qualified… but… this is a puzzling and odd issue. This is an issue that likely has a…
“I never thought to check THAT! What an unusual situation!” -solution. 
SO… Wingy asks goofy investigation questions to possibly help find elusive cause. Ignore me, as needed. 