Thank you for your response.
Disabling parts of my flow looks like a lot of work, given the many number of tabs involved. I think it's especially hard because there seems no consistent way to reproduce the warning messages in my case, so maybe it's not a big problem after all?
Anyhow, I'm using lots of modules, so posting the list here might help cross-reference it with others to narrow down a (or more) possible suspects:
"md5": "^2.2.1",
"node-red-contrib--cron-pkjq": "0.0.1",
"node-red-contrib-bigtimer": "~2.7.3",
"node-red-contrib-bool-gate": "~1.0.2",
"node-red-contrib-cast": "~0.2.17",
"node-red-contrib-castv2": "~4.0.3",
"node-red-contrib-eiscp": "0.3.3",
"node-red-contrib-elasticsearch-jupalcf": "~1.1.14",
"node-red-contrib-harmony-websocket": "~2.2.6",
"node-red-contrib-huemagic": "~3.0.0",
"node-red-contrib-influxdb": "~0.5.4",
"node-red-contrib-json": "~0.2.0",
"node-red-contrib-moment": "~4.0.0",
"node-red-contrib-msg-speed": "~2.0.0",
"node-red-contrib-openhab3": "^1.3.3",
"node-red-contrib-simpletime": "~2.10.0",
"node-red-contrib-smb": "~1.2.0",
"node-red-contrib-solaredge": "~0.1.0",
"node-red-contrib-throttle": "~0.1.6",
"node-red-contrib-timed-counter": "0.0.4",
"node-red-contrib-timeframerlt": "~0.3.1",
"node-red-node-aws": "~0.2.0",
"node-red-node-darksky": "~0.1.19",
"node-red-node-email": "~1.8.3",
"node-red-node-random": "~0.3.1",
"node-red-node-rbe": "~0.2.9",
"regression-fork-norounding": "1.4.0-11",
"thingzi-logic-timers": "~1.1.3",
"trend": "0.3.0"