Using same parallel function sometimes takes longer to complete than usual

[NOTEKAMI (NOT)]

Im using parallel to create own ZonePlus (more optimized) and almost completed it.
But i have this issue?
Any ideas what this could be related to?

-- Parallel worker code:
local Actor = script:GetActor()

local function GetPartsInPart(Part: BasePart, Params: OverlapParams?)
	return workspace:GetPartsInPart(Part, Params)
end

local function GetPartBoundsInBox(Part: Part, Params: OverlapParams?)
	return workspace:GetPartBoundsInBox(Part.CFrame, Part.Size, Params)
end

local function GetPartBoundsInRadius(Part: Part, Params: OverlapParams?)
	return workspace:GetPartBoundsInRadius(Part.Position, Part.Size.X, Params)
end

local function GetPartsMethod(BasePart: BasePart)
	if BasePart:IsA(`Part`) then
		if BasePart.Shape == Enum.PartType.Block then
			return GetPartBoundsInBox
		elseif BasePart.Shape == Enum.PartType.Ball then
			return GetPartBoundsInRadius
		end
	end
	
	return GetPartsInPart
end

Actor:BindToMessageParallel(`Step`, function(BindableEvent: BindableEvent, Container: BasePart, Params: OverlapParams?, Index: any)
	debug.profilebegin(`Step`)
	BindableEvent:Fire(Index, GetPartsMethod(Container)(Container, Params))
	debug.profileend()
end)

[A_Mp5 (amp)]

Seeing how the hiccup is the same accross all workers, I would assume it’s an engine thing
(but it is also consistently the first block on the thread. caching?)