@cyborg I'm not sure that is the same issue. You might be better served creating a separate ticket.

It might be related, it might not. Do you get constant UI switching? Does your issue only happen when using two of your various input methods at once? If you think it is UI/Input switching related, you could try this mod I made and force UI hints from auto switching (vanilla) to either KBM or Controller :
https://reforger.armaplatform.com/workshop/F094FB63FA584B1C-PSYControls-Beta

If it does help, I could potentially extend the mod to better cater for steering wheels, ect, but I'd need some more info, as I don't use those myself or have them on hand.

Also, does public Reforger 1.8.0.13 ArmaReforgerSteamDiag.exe include an enabled Tracy client? If so, what activation method, endpoint and viewer/protocol version are required, and does it expose native execution or only script-VM zones?

Still reproducible on 1.8.0.13 with Azeron and Xbox controllers. Testing points to repeated input-device switching and UI hint refreshes as significant contributors: bypassing SCR_InputButtonComponent.OnInputDeviceUserChanged substantially reduced hitching, and restoring it brought the hitching back. I made a mod that keeps affected on-screen button prompts in keyboard/mouse style instead of automatically switching between keyboard/mouse and controller icons. Standalone testing reduced P99 frame time from 12.54 ms to 9.79 ms—about 22%, returning to 12.44 ms when automatic switching was restored. Residual irregularity remains: 9.79 ms P99 versus 8.78 ms with WASD+mouse—about 11.5% higher. Captures, event logs, test procedures and diagnostic code are available if useful.

Can you please list the duplicated issue, so that I can comment there? I think when issues are closed or listed as duplicate, the duplicated issue should be linked or cited so that the people can find the original issue in case they have questions, comments or addtional feedback.