About 20% or more FPS values are wildly incorrect when FPS limit and Vsync set, but ok when not

[taosecurity]

Describe the bug
I've been testing game performance with 60 seconds of logging in MangoHud. When testing with fps_limit=141 vsync=3, about 700 of my over 4700 results were far too high -- with 97% FPS stats over 1500.

However, if I set fps_limit=0 vsync=1 I get normal results.

List relevant hardware/software information

• Linux Mint 22
• MangoHud version 0.7.2
• GPU Nvidia 4070 Ti Super

To Reproduce
Steps to reproduce the behavior:
Run a 60 second logging test with fps_limit=141 vsync=3 and see results.

Expected behavior
I should get FPS counts in the hundreds, not thousands.

Screenshots
Here is a sample using fps_limit=141 vsync=3

https://flightlessmango.com/games/154035/logs/5998

[
{
"0.1% Min FPS": 29.7,
"1% Min FPS": 35.5,
"97% Percentile FPS": 1508.2,
"Average FPS": 78.9,
"GPU Load": 96.8,
"CPU Load": 60,
"Average Frame Time": 12.7,
"Average GPU Temp": 66,
"Average CPU Temp": 71,
"Average VRAM Used": 10.3,
"Average RAM Used": 15.8,
"Average Swap Used": 0,
"Peak GPU Load": 97,
"Peak CPU Load": 78,
"Peak GPU Temp": 69,
"Peak CPU Temp": 76,
"Peak VRAM Used": 10.3,
"Peak RAM Used": 15.9,
"Peak Swap Used": 0
}
]

I ran several others with similar results.

Here is a sample using fps_limit=0 vsync=1

https://flightlessmango.com/games/154035/logs/6015

[
{
"0.1% Min FPS": 37.1,
"1% Min FPS": 47.7,
"97% Percentile FPS": 149.7,
"Average FPS": 79.2,
"GPU Load": 95,
"CPU Load": 65.1,
"Average Frame Time": 12.6,
"Average GPU Temp": 58,
"Average CPU Temp": 65,
"Average VRAM Used": 6.6,
"Average RAM Used": 14.5,
"Average Swap Used": 0,
"Peak GPU Load": 96,
"Peak CPU Load": 87.8,
"Peak GPU Temp": 62,
"Peak CPU Temp": 75,
"Peak VRAM Used": 6.6,
"Peak RAM Used": 14.6,
"Peak Swap Used": 0
}
]

Additional context
I use a 4k monitor at 144 MHz.