Prints on Instances (and Instance properties) arriving out of sequence under deeply nested threads

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1

As early as April 14 2026 at 11:30am PST, I was debugging an issue with my game in Roblox Studio, placing prints around my code as one does, and I noticed that prints were arriving in a backwards sequence. I am unable to debug parts of my game as a result of this problem.

I was unable to reproduce an isolated instance of the prints arriving in backwards, despite my best efforts to download the affected place and reproduce the issue itself, but the behavior remains. I’ve provided more context in the private message attached/associated with this bug report.

Expected behavior

Prints should arrive in an expected manner, line by line, in an ascending order.

A private message is associated with this bug report

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2

I’m currently having this same problem, I think — print statements printing out-of-order. Never seen this before.

Edit: It seems that print statements that were passed arguments were printing later than print statements that weren’t passed arguments. Example:

local playerName = "Bob"
print("Hi", playerName)
print("Apple")

Resulting in the output:

Apple
Hi Bob
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3

I can confirm that I am also running into prints being printed out of order as well. I do have a reproduction that works sometimes as long as SignalBehavior is set to Deferred:

local bindable = Instance.new("BindableEvent")

bindable.Event:Once(function() 
	print("reference:", game)
	print("id:", game:GetDebugId())
	print("last") 
end)

bindable:Fire()

which can occasionally give you:

  10:12:19.445  id: 0_2376278
  10:12:19.445  last
  10:12:19.444  reference: Place1
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4

(cc @Sonderlyw @mvyasu)

I think the behavior the three of us are experiencing is extremely varied in nature based on what I can gather from your experiences. In my case, this behavior appears under a callstack that contains multiple nested threads where the prints occur, and in a game whose SignalBehavior is set to Immediate mode.

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5

Hello,
We have recently added fixes that may have resolved this issue. Please try your cases again, and tell me if you still run into this issue.
Thanks,
IcyTides

6

Just tried my own case again; the print statements seem to print in the expected order now.

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