#112 Consistent Error in ChangeFPS

[SilverbackNet]

Avidemux 2.18.1 x64 (from site downloads)
Win10 x64
Nowhere near running out of RAM or VRAM

ChangeFPS errors out when saving things once in a while. It is reproducible once it happens, so I've attached a test case. Adjusting the numbers slightly doesn't seem to help, but adjusting the start (A) marker does. Most of the time, ChangeFPS works great with no problem.

Error is:

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Info
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Too short

The saved video is incomplete. The error occured at 00:00:39,889 (66). This may happen as result of invalid time stamps in the video.

Error -22 ("Invalid argument")
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OK   
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