In D15100#416396, @tomek wrote:

Could you share a flow.org/try repro to experiment with?

I simplified the types a little, but the gist and the error is the same.
Have fun

Indeed, this seems like an issue with Flow. The simplest repro: https://flow.org/try/#1N4Igxg9gdgZglgcxALlAIwIZoKYBsD6uEEAztvhgE6UYCe+JADpdhgCYowa5kA0I2KAFcAtiRQAXSkOz9sADwxgJ+NPTbYuQ3BMnTZA+Y2yU4IwRO4A6SFBIrGVDGM7c+h46fNRLuKxJIGWh8MeT0ZfhYlCStpHzNsFBAMIQkIEQwJODAQfiEyfBE4eWw2fDgofDBMsAALfAA3KjgsXGxxZC4eAw0G-GhcWn9aY3wWZldu-g1mbGqJUoBaCRHEzrcDEgBrbAk62kXhXFxJ923d-cPRHEpTgyEoMDaqZdW7vKgoOfaSKgOKpqmDA+d4gB5fMA-P6LCCMLLQbiLOoYCqgh6-GDYRYIXYLSgkRZkCR4jpddwPfJLZjpOBkO4AX34kA0SRWxgABAB5NAAK3ZAF52cAADpQdnsgDUGGQ7OEIhuvFF4olaBlcoVovpAG5RaLbPZ2RIZdy+YKRWL2dL2QBGRUW1XsgBMdvpuqgGieVGw7P1EnZJHZMoAJABpbC0EgAHhNAD4dVA9dADRJHcbeQKhUr2VYcxI7eKANokAC6MoArC6tbkQA0TCQ4NAkg0AAxWR0ANgAnFZrSB6UA
It can be fixed by making ThreadTimestamps inexact, but it will weaken our typesystem. Let's ignore the error, but please be specific in which error you're silencing. (use $FlowIgnore)