I ran into this with some new unbeaconed labs, where the entity's speed bonus, as reported by both the tooltip and in the lua terminal was 1.1 (+110%). My research speed bonus from the lab speed techs was 2.5 (+250%) and the labs had 4 prod 2 mods for a -0.4 (-40%) speed modifier from them, so when Parallel Research tried to "correct" the speed bonus, it multiplied by 1 + 1.1 - 2.5 = -0.4. When it came time to perform research, this resulted in Parallel Research trying to give negative progress to the new tech it was just starting to research, making the game crash.
My best guess for what happened was that entity.speed_bonus was fixed at some point and we just didn't notice. The listed speed also matches the base speed times 1 + the listed bonus. Doing the math manually gives `(1 + -0.4)*(1 + 2.5) - 1 = 0.6 * 3.5 - 1 = 2.1 - 1 = 1.1, like the tooltip and property read from lua.
