[BUG] Faulty "Use Last Keyframe?" Toggle in Timelines

Development Programming & Scripting Blueprint
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1

This is a followup to the following bug report:

After some testing, I think I’ve narrowed down the hiding spot of this elusive bug to the Use Last Keyframe? Toggle. Here’s the steps to reproduce the bug:

1: Launch Unreal Engine 4.11.2

2: Create project from starter template - First Person

3: Open First Person Character blueprint

4: Add timeline

5: Connect Play from Start of Timeline_0 to Event BeginPlay

6: Connect Finished of Timeline_0 to Set GunOffset

7: Assign a breakpoint to Set GunOffset

8: Open Timeline_0 and add Float Track

9: Add Keyframe at time 0.364, value 0.077 (On further testing, Keyframe times and values don’t seem to matter)

10: Add Keyframe at time 6.991, value 2.039 (Leave Length at 5.00)

11: Toggle Use Last Keyframe? on

12: Play. Breakpoint triggers at 6.991 seconds from begin of play

13: Stop Play and go back into Timeline_0 and toggle Use Last Keyframe? off

14: Play. Breakpoint triggers at 6.991 seconds from begin of play

Breakpoint should trigger at 5.00 seconds from begin of play

15: Stop Play and go back into Timeline_0 and set Length to 2.00

16: Play. Breakpoint triggers at 6.991 seconds from begin of play

Breakpoint should trigger at 2.00 seconds from begin of play

17: Stop Play, go back into Timeline_0 and delete Key at time 6.991

18: Play. Breakpoint triggers at 0.364 seconds from begin play

Breakpoint should trigger at 2.00 seconds from begin of play

2

Hello ElderTwin,

I have ran the test above on the 4.12.1 version of the engine and this issue does not appear to be happening. Could you try to reproduce this issue in the 4.12. version of the engine and let me know if you can reproduce this issue? If so, could you provide an updated version of your reproduction steps so that I can reproduce this issue on our end?

3

Hello ElderTwin,

We have not heard back from you in a few days, so we are marking this post as Resolved for tracking purposes. If you are still experiencing the issue you reported, please respond to this message with additional information and we will offer further assistance.

Thank you.

4

Okay, I did end up thinking of a way to provide more detail:

Hope it helps

5

Finally got around to updating to version 4.12.2 and I was able to reproduce these results several more times. Made a video recording if it helps:

During two of my trials, I had hit play on step 12 before realizing that I had forgotten step 11. When I rolled the trial back to step 11 and continued from there, I wasn’t able to reproduce the bug.

6

After taking a look at the video provided I was able to reproduce this issue on our end. I have written up a report ( UE-32081) and I have submitted it to the developers for further consideration. I will provide updates with any pertinent information as it becomes available. Thank you for your time and information.

Make it a great day